-/*P:100 This is the Launcher code, a simple program which lays out the
- * "physical" memory for the new Guest by mapping the kernel image and
- * the virtual devices, then opens /dev/lguest to tell the kernel
- * about the Guest and control it. :*/
+/*P:100
+ * This is the Launcher code, a simple program which lays out the "physical"
+ * memory for the new Guest by mapping the kernel image and the virtual
+ * devices, then opens /dev/lguest to tell the kernel about the Guest and
+ * control it.
+:*/
#define _LARGEFILE64_SOURCE
#define _GNU_SOURCE
#include <stdio.h>
#include "linux/virtio_rng.h"
#include "linux/virtio_ring.h"
#include "asm/bootparam.h"
-/*L:110 We can ignore the 39 include files we need for this program, but I do
- * want to draw attention to the use of kernel-style types.
+/*L:110
+ * We can ignore the 39 include files we need for this program, but I do want
+ * to draw attention to the use of kernel-style types.
*
* As Linus said, "C is a Spartan language, and so should your naming be." I
* like these abbreviations, so we define them here. Note that u64 is always
* unsigned long long, which works on all Linux systems: this means that we can
- * use %llu in printf for any u64. */
+ * use %llu in printf for any u64.
+ */
typedef unsigned long long u64;
typedef uint32_t u32;
typedef uint16_t u16;
/* This will occupy 3 pages: it must be a power of 2. */
#define VIRTQUEUE_NUM 256
-/*L:120 verbose is both a global flag and a macro. The C preprocessor allows
- * this, and although I wouldn't recommend it, it works quite nicely here. */
+/*L:120
+ * verbose is both a global flag and a macro. The C preprocessor allows
+ * this, and although I wouldn't recommend it, it works quite nicely here.
+ */
static bool verbose;
#define verbose(args...) \
do { if (verbose) printf(args); } while(0)
/* A single linked list of devices. */
struct device *dev;
- /* And a pointer to the last device for easy append and also for
- * configuration appending. */
+ /* And a pointer to the last device for easy append. */
struct device *lastdev;
};
/* The original tty settings to restore on exit. */
static struct termios orig_term;
-/* We have to be careful with barriers: our devices are all run in separate
+/*
+ * We have to be careful with barriers: our devices are all run in separate
* threads and so we need to make sure that changes visible to the Guest happen
- * in precise order. */
+ * in precise order.
+ */
#define wmb() __asm__ __volatile__("" : : : "memory")
#define mb() __asm__ __volatile__("" : : : "memory")
-/* Convert an iovec element to the given type.
+/*
+ * Convert an iovec element to the given type.
*
* This is a fairly ugly trick: we need to know the size of the type and
* alignment requirement to check the pointer is kosher. It's also nice to
* have the name of the type in case we report failure.
*
* Typing those three things all the time is cumbersome and error prone, so we
- * have a macro which sets them all up and passes to the real function. */
+ * have a macro which sets them all up and passes to the real function.
+ */
#define convert(iov, type) \
((type *)_convert((iov), sizeof(type), __alignof__(type), #type))
/* Wrapper for the last available index. Makes it easier to change. */
#define lg_last_avail(vq) ((vq)->last_avail_idx)
-/* The virtio configuration space is defined to be little-endian. x86 is
- * little-endian too, but it's nice to be explicit so we have these helpers. */
+/*
+ * The virtio configuration space is defined to be little-endian. x86 is
+ * little-endian too, but it's nice to be explicit so we have these helpers.
+ */
#define cpu_to_le16(v16) (v16)
#define cpu_to_le32(v32) (v32)
#define cpu_to_le64(v64) (v64)
+ dev->num_vq * sizeof(struct lguest_vqconfig);
}
-/*L:100 The Launcher code itself takes us out into userspace, that scary place
- * where pointers run wild and free! Unfortunately, like most userspace
- * programs, it's quite boring (which is why everyone likes to hack on the
- * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it
- * will get you through this section. Or, maybe not.
+/*L:100
+ * The Launcher code itself takes us out into userspace, that scary place where
+ * pointers run wild and free! Unfortunately, like most userspace programs,
+ * it's quite boring (which is why everyone likes to hack on the kernel!).
+ * Perhaps if you make up an Lguest Drinking Game at this point, it will get
+ * you through this section. Or, maybe not.
*
* The Launcher sets up a big chunk of memory to be the Guest's "physical"
* memory and stores it in "guest_base". In other words, Guest physical ==
*
* This can be tough to get your head around, but usually it just means that we
* use these trivial conversion functions when the Guest gives us it's
- * "physical" addresses: */
+ * "physical" addresses:
+ */
static void *from_guest_phys(unsigned long addr)
{
return guest_base + addr;
* Loading the Kernel.
*
* We start with couple of simple helper routines. open_or_die() avoids
- * error-checking code cluttering the callers: */
+ * error-checking code cluttering the callers:
+ */
static int open_or_die(const char *name, int flags)
{
int fd = open(name, flags);
int fd = open_or_die("/dev/zero", O_RDONLY);
void *addr;
- /* We use a private mapping (ie. if we write to the page, it will be
- * copied). */
+ /*
+ * We use a private mapping (ie. if we write to the page, it will be
+ * copied).
+ */
addr = mmap(NULL, getpagesize() * num,
PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
if (addr == MAP_FAILED)
return addr;
}
-/* This routine is used to load the kernel or initrd. It tries mmap, but if
+/*
+ * This routine is used to load the kernel or initrd. It tries mmap, but if
* that fails (Plan 9's kernel file isn't nicely aligned on page boundaries),
- * it falls back to reading the memory in. */
+ * it falls back to reading the memory in.
+ */
static void map_at(int fd, void *addr, unsigned long offset, unsigned long len)
{
ssize_t r;
- /* We map writable even though for some segments are marked read-only.
+ /*
+ * We map writable even though for some segments are marked read-only.
* The kernel really wants to be writable: it patches its own
* instructions.
*
* MAP_PRIVATE means that the page won't be copied until a write is
* done to it. This allows us to share untouched memory between
- * Guests. */
+ * Guests.
+ */
if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED)
return;
err(1, "Reading offset %lu len %lu gave %zi", offset, len, r);
}
-/* This routine takes an open vmlinux image, which is in ELF, and maps it into
+/*
+ * This routine takes an open vmlinux image, which is in ELF, and maps it into
* the Guest memory. ELF = Embedded Linking Format, which is the format used
* by all modern binaries on Linux including the kernel.
*
* address. We use the physical address; the Guest will map itself to the
* virtual address.
*
- * We return the starting address. */
+ * We return the starting address.
+ */
static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr)
{
Elf32_Phdr phdr[ehdr->e_phnum];
unsigned int i;
- /* Sanity checks on the main ELF header: an x86 executable with a
- * reasonable number of correctly-sized program headers. */
+ /*
+ * Sanity checks on the main ELF header: an x86 executable with a
+ * reasonable number of correctly-sized program headers.
+ */
if (ehdr->e_type != ET_EXEC
|| ehdr->e_machine != EM_386
|| ehdr->e_phentsize != sizeof(Elf32_Phdr)
|| ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr))
errx(1, "Malformed elf header");
- /* An ELF executable contains an ELF header and a number of "program"
+ /*
+ * An ELF executable contains an ELF header and a number of "program"
* headers which indicate which parts ("segments") of the program to
- * load where. */
+ * load where.
+ */
/* We read in all the program headers at once: */
if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0)
if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr))
err(1, "Reading program headers");
- /* Try all the headers: there are usually only three. A read-only one,
- * a read-write one, and a "note" section which we don't load. */
+ /*
+ * Try all the headers: there are usually only three. A read-only one,
+ * a read-write one, and a "note" section which we don't load.
+ */
for (i = 0; i < ehdr->e_phnum; i++) {
/* If this isn't a loadable segment, we ignore it */
if (phdr[i].p_type != PT_LOAD)
return ehdr->e_entry;
}
-/*L:150 A bzImage, unlike an ELF file, is not meant to be loaded. You're
- * supposed to jump into it and it will unpack itself. We used to have to
- * perform some hairy magic because the unpacking code scared me.
+/*L:150
+ * A bzImage, unlike an ELF file, is not meant to be loaded. You're supposed
+ * to jump into it and it will unpack itself. We used to have to perform some
+ * hairy magic because the unpacking code scared me.
*
* Fortunately, Jeremy Fitzhardinge convinced me it wasn't that hard and wrote
* a small patch to jump over the tricky bits in the Guest, so now we just read
- * the funky header so we know where in the file to load, and away we go! */
+ * the funky header so we know where in the file to load, and away we go!
+ */
static unsigned long load_bzimage(int fd)
{
struct boot_params boot;
/* Modern bzImages get loaded at 1M. */
void *p = from_guest_phys(0x100000);
- /* Go back to the start of the file and read the header. It should be
- * a Linux boot header (see Documentation/x86/i386/boot.txt) */
+ /*
+ * Go back to the start of the file and read the header. It should be
+ * a Linux boot header (see Documentation/x86/i386/boot.txt)
+ */
lseek(fd, 0, SEEK_SET);
read(fd, &boot, sizeof(boot));
return boot.hdr.code32_start;
}
-/*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels
+/*L:140
+ * Loading the kernel is easy when it's a "vmlinux", but most kernels
* come wrapped up in the self-decompressing "bzImage" format. With a little
- * work, we can load those, too. */
+ * work, we can load those, too.
+ */
static unsigned long load_kernel(int fd)
{
Elf32_Ehdr hdr;
return load_bzimage(fd);
}
-/* This is a trivial little helper to align pages. Andi Kleen hated it because
+/*
+ * This is a trivial little helper to align pages. Andi Kleen hated it because
* it calls getpagesize() twice: "it's dumb code."
*
* Kernel guys get really het up about optimization, even when it's not
- * necessary. I leave this code as a reaction against that. */
+ * necessary. I leave this code as a reaction against that.
+ */
static inline unsigned long page_align(unsigned long addr)
{
/* Add upwards and truncate downwards. */
return ((addr + getpagesize()-1) & ~(getpagesize()-1));
}
-/*L:180 An "initial ram disk" is a disk image loaded into memory along with
- * the kernel which the kernel can use to boot from without needing any
- * drivers. Most distributions now use this as standard: the initrd contains
- * the code to load the appropriate driver modules for the current machine.
+/*L:180
+ * An "initial ram disk" is a disk image loaded into memory along with the
+ * kernel which the kernel can use to boot from without needing any drivers.
+ * Most distributions now use this as standard: the initrd contains the code to
+ * load the appropriate driver modules for the current machine.
*
* Importantly, James Morris works for RedHat, and Fedora uses initrds for its
- * kernels. He sent me this (and tells me when I break it). */
+ * kernels. He sent me this (and tells me when I break it).
+ */
static unsigned long load_initrd(const char *name, unsigned long mem)
{
int ifd;
if (fstat(ifd, &st) < 0)
err(1, "fstat() on initrd '%s'", name);
- /* We map the initrd at the top of memory, but mmap wants it to be
- * page-aligned, so we round the size up for that. */
+ /*
+ * We map the initrd at the top of memory, but mmap wants it to be
+ * page-aligned, so we round the size up for that.
+ */
len = page_align(st.st_size);
map_at(ifd, from_guest_phys(mem - len), 0, st.st_size);
- /* Once a file is mapped, you can close the file descriptor. It's a
- * little odd, but quite useful. */
+ /*
+ * Once a file is mapped, you can close the file descriptor. It's a
+ * little odd, but quite useful.
+ */
close(ifd);
verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len);
}
/*:*/
-/* Simple routine to roll all the commandline arguments together with spaces
- * between them. */
+/*
+ * Simple routine to roll all the commandline arguments together with spaces
+ * between them.
+ */
static void concat(char *dst, char *args[])
{
unsigned int i, len = 0;
dst[len] = '\0';
}
-/*L:185 This is where we actually tell the kernel to initialize the Guest. We
+/*L:185
+ * This is where we actually tell the kernel to initialize the Guest. We
* saw the arguments it expects when we looked at initialize() in lguest_user.c:
* the base of Guest "physical" memory, the top physical page to allow and the
- * entry point for the Guest. */
+ * entry point for the Guest.
+ */
static void tell_kernel(unsigned long start)
{
unsigned long args[] = { LHREQ_INITIALIZE,
static void *_check_pointer(unsigned long addr, unsigned int size,
unsigned int line)
{
- /* We have to separately check addr and addr+size, because size could
- * be huge and addr + size might wrap around. */
+ /*
+ * We have to separately check addr and addr+size, because size could
+ * be huge and addr + size might wrap around.
+ */
if (addr >= guest_limit || addr + size >= guest_limit)
errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr);
- /* We return a pointer for the caller's convenience, now we know it's
- * safe to use. */
+ /*
+ * We return a pointer for the caller's convenience, now we know it's
+ * safe to use.
+ */
return from_guest_phys(addr);
}
/* A macro which transparently hands the line number to the real function. */
#define check_pointer(addr,size) _check_pointer(addr, size, __LINE__)
-/* Each buffer in the virtqueues is actually a chain of descriptors. This
+/*
+ * Each buffer in the virtqueues is actually a chain of descriptors. This
* function returns the next descriptor in the chain, or vq->vring.num if we're
- * at the end. */
+ * at the end.
+ */
static unsigned next_desc(struct vring_desc *desc,
unsigned int i, unsigned int max)
{
err(1, "Triggering irq %i", vq->config.irq);
}
-/* This looks in the virtqueue and for the first available buffer, and converts
+/*
+ * This looks in the virtqueue and for the first available buffer, and converts
* it to an iovec for convenient access. Since descriptors consist of some
* number of output then some number of input descriptors, it's actually two
* iovecs, but we pack them into one and note how many of each there were.
*
- * This function returns the descriptor number found. */
+ * This function returns the descriptor number found.
+ */
static unsigned wait_for_vq_desc(struct virtqueue *vq,
struct iovec iov[],
unsigned int *out_num, unsigned int *in_num)
/* OK, now we need to know about added descriptors. */
vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
- /* They could have slipped one in as we were doing that: make
- * sure it's written, then check again. */
+ /*
+ * They could have slipped one in as we were doing that: make
+ * sure it's written, then check again.
+ */
mb();
if (last_avail != vq->vring.avail->idx) {
vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
errx(1, "Guest moved used index from %u to %u",
last_avail, vq->vring.avail->idx);
- /* Grab the next descriptor number they're advertising, and increment
- * the index we've seen. */
+ /*
+ * Grab the next descriptor number they're advertising, and increment
+ * the index we've seen.
+ */
head = vq->vring.avail->ring[last_avail % vq->vring.num];
lg_last_avail(vq)++;
desc = vq->vring.desc;
i = head;
- /* If this is an indirect entry, then this buffer contains a descriptor
- * table which we handle as if it's any normal descriptor chain. */
+ /*
+ * If this is an indirect entry, then this buffer contains a descriptor
+ * table which we handle as if it's any normal descriptor chain.
+ */
if (desc[i].flags & VRING_DESC_F_INDIRECT) {
if (desc[i].len % sizeof(struct vring_desc))
errx(1, "Invalid size for indirect buffer table");
if (desc[i].flags & VRING_DESC_F_WRITE)
(*in_num)++;
else {
- /* If it's an output descriptor, they're all supposed
- * to come before any input descriptors. */
+ /*
+ * If it's an output descriptor, they're all supposed
+ * to come before any input descriptors.
+ */
if (*in_num)
errx(1, "Descriptor has out after in");
(*out_num)++;
return head;
}
-/* After we've used one of their buffers, we tell them about it. We'll then
- * want to send them an interrupt, using trigger_irq(). */
+/*
+ * After we've used one of their buffers, we tell them about it. We'll then
+ * want to send them an interrupt, using trigger_irq().
+ */
static void add_used(struct virtqueue *vq, unsigned int head, int len)
{
struct vring_used_elem *used;
- /* The virtqueue contains a ring of used buffers. Get a pointer to the
- * next entry in that used ring. */
+ /*
+ * The virtqueue contains a ring of used buffers. Get a pointer to the
+ * next entry in that used ring.
+ */
used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
used->id = head;
used->len = len;
/*
* The Console
*
- * We associate some data with the console for our exit hack. */
+ * We associate some data with the console for our exit hack.
+ */
struct console_abort
{
/* How many times have they hit ^C? */
if (len <= 0) {
/* Ran out of input? */
warnx("Failed to get console input, ignoring console.");
- /* For simplicity, dying threads kill the whole Launcher. So
- * just nap here. */
+ /*
+ * For simplicity, dying threads kill the whole Launcher. So
+ * just nap here.
+ */
for (;;)
pause();
}
add_used_and_trigger(vq, head, len);
- /* Three ^C within one second? Exit.
+ /*
+ * Three ^C within one second? Exit.
*
* This is such a hack, but works surprisingly well. Each ^C has to
* be in a buffer by itself, so they can't be too fast. But we check
* that we get three within about a second, so they can't be too
- * slow. */
+ * slow.
+ */
if (len != 1 || ((char *)iov[0].iov_base)[0] != 3) {
abort->count = 0;
return;
return select(fd+1, &fdset, NULL, NULL, &zero) != 1;
}
-/* This is where we handle packets coming in from the tun device to our
- * Guest. */
+/* This handles packets coming in from the tun device to our Guest. */
static void net_input(struct virtqueue *vq)
{
int len;
return 0;
}
-/* When a child dies, we kill our entire process group with SIGTERM. This
- * also has the side effect that the shell restores the console for us! */
+/*
+ * When a child dies, we kill our entire process group with SIGTERM. This
+ * also has the side effect that the shell restores the console for us!
+ */
static void kill_launcher(int signal)
{
kill(0, SIGTERM);
static void create_thread(struct virtqueue *vq)
{
- /* Create stack for thread and run it. Since stack grows
- * upwards, we point the stack pointer to the end of this
- * region. */
+ /*
+ * Create stack for thread and run it. Since the stack grows upwards,
+ * we point the stack pointer to the end of this region.
+ */
char *stack = malloc(32768);
unsigned long args[] = { LHREQ_EVENTFD,
vq->config.pfn*getpagesize(), 0 };
}
}
- /* Early console write is done using notify on a nul-terminated string
- * in Guest memory. */
+ /*
+ * Early console write is done using notify on a nul-terminated string
+ * in Guest memory. It's also great for hacking debugging messages
+ * into a Guest.
+ */
if (addr >= guest_limit)
errx(1, "Bad NOTIFY %#lx", addr);
* routines to allocate and manage them.
*/
-/* The layout of the device page is a "struct lguest_device_desc" followed by a
+/*
+ * The layout of the device page is a "struct lguest_device_desc" followed by a
* number of virtqueue descriptors, then two sets of feature bits, then an
* array of configuration bytes. This routine returns the configuration
- * pointer. */
+ * pointer.
+ */
static u8 *device_config(const struct device *dev)
{
return (void *)(dev->desc + 1)
+ dev->feature_len * 2;
}
-/* This routine allocates a new "struct lguest_device_desc" from descriptor
+/*
+ * This routine allocates a new "struct lguest_device_desc" from descriptor
* table page just above the Guest's normal memory. It returns a pointer to
- * that descriptor. */
+ * that descriptor.
+ */
static struct lguest_device_desc *new_dev_desc(u16 type)
{
struct lguest_device_desc d = { .type = type };
return memcpy(p, &d, sizeof(d));
}
-/* Each device descriptor is followed by the description of its virtqueues. We
- * specify how many descriptors the virtqueue is to have. */
+/*
+ * Each device descriptor is followed by the description of its virtqueues. We
+ * specify how many descriptors the virtqueue is to have.
+ */
static void add_virtqueue(struct device *dev, unsigned int num_descs,
void (*service)(struct virtqueue *))
{
/* Initialize the vring. */
vring_init(&vq->vring, num_descs, p, LGUEST_VRING_ALIGN);
- /* Append virtqueue to this device's descriptor. We use
+ /*
+ * Append virtqueue to this device's descriptor. We use
* device_config() to get the end of the device's current virtqueues;
* we check that we haven't added any config or feature information
- * yet, otherwise we'd be overwriting them. */
+ * yet, otherwise we'd be overwriting them.
+ */
assert(dev->desc->config_len == 0 && dev->desc->feature_len == 0);
memcpy(device_config(dev), &vq->config, sizeof(vq->config));
dev->num_vq++;
verbose("Virtqueue page %#lx\n", to_guest_phys(p));
- /* Add to tail of list, so dev->vq is first vq, dev->vq->next is
- * second. */
+ /*
+ * Add to tail of list, so dev->vq is first vq, dev->vq->next is
+ * second.
+ */
for (i = &dev->vq; *i; i = &(*i)->next);
*i = vq;
}
-/* The first half of the feature bitmask is for us to advertise features. The
- * second half is for the Guest to accept features. */
+/*
+ * The first half of the feature bitmask is for us to advertise features. The
+ * second half is for the Guest to accept features.
+ */
static void add_feature(struct device *dev, unsigned bit)
{
u8 *features = get_feature_bits(dev);
features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
}
-/* This routine sets the configuration fields for an existing device's
+/*
+ * This routine sets the configuration fields for an existing device's
* descriptor. It only works for the last device, but that's OK because that's
- * how we use it. */
+ * how we use it.
+ */
static void set_config(struct device *dev, unsigned len, const void *conf)
{
/* Check we haven't overflowed our single page. */
assert(dev->desc->config_len == len);
}
-/* This routine does all the creation and setup of a new device, including
+/*
+ * This routine does all the creation and setup of a new device, including
* calling new_dev_desc() to allocate the descriptor and device memory.
*
- * See what I mean about userspace being boring? */
+ * See what I mean about userspace being boring?
+ */
static struct device *new_device(const char *name, u16 type)
{
struct device *dev = malloc(sizeof(*dev));
dev->num_vq = 0;
dev->running = false;
- /* Append to device list. Prepending to a single-linked list is
+ /*
+ * Append to device list. Prepending to a single-linked list is
* easier, but the user expects the devices to be arranged on the bus
* in command-line order. The first network device on the command line
- * is eth0, the first block device /dev/vda, etc. */
+ * is eth0, the first block device /dev/vda, etc.
+ */
if (devices.lastdev)
devices.lastdev->next = dev;
else
return dev;
}
-/* Our first setup routine is the console. It's a fairly simple device, but
- * UNIX tty handling makes it uglier than it could be. */
+/*
+ * Our first setup routine is the console. It's a fairly simple device, but
+ * UNIX tty handling makes it uglier than it could be.
+ */
static void setup_console(void)
{
struct device *dev;
/* If we can save the initial standard input settings... */
if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
struct termios term = orig_term;
- /* Then we turn off echo, line buffering and ^C etc. We want a
- * raw input stream to the Guest. */
+ /*
+ * Then we turn off echo, line buffering and ^C etc: We want a
+ * raw input stream to the Guest.
+ */
term.c_lflag &= ~(ISIG|ICANON|ECHO);
tcsetattr(STDIN_FILENO, TCSANOW, &term);
}
dev->priv = malloc(sizeof(struct console_abort));
((struct console_abort *)dev->priv)->count = 0;
- /* The console needs two virtqueues: the input then the output. When
+ /*
+ * The console needs two virtqueues: the input then the output. When
* they put something the input queue, we make sure we're listening to
* stdin. When they put something in the output queue, we write it to
- * stdout. */
+ * stdout.
+ */
add_virtqueue(dev, VIRTQUEUE_NUM, console_input);
add_virtqueue(dev, VIRTQUEUE_NUM, console_output);
}
/*:*/
-/*M:010 Inter-guest networking is an interesting area. Simplest is to have a
+/*M:010
+ * Inter-guest networking is an interesting area. Simplest is to have a
* --sharenet=<name> option which opens or creates a named pipe. This can be
* used to send packets to another guest in a 1:1 manner.
*
* multiple inter-guest channels behind one interface, although it would
* require some manner of hotplugging new virtio channels.
*
- * Finally, we could implement a virtio network switch in the kernel. :*/
+ * Finally, we could implement a virtio network switch in the kernel.
+:*/
static u32 str2ip(const char *ipaddr)
{
mac[5] = m[5];
}
-/* This code is "adapted" from libbridge: it attaches the Host end of the
+/*
+ * This code is "adapted" from libbridge: it attaches the Host end of the
* network device to the bridge device specified by the command line.
*
* This is yet another James Morris contribution (I'm an IP-level guy, so I
- * dislike bridging), and I just try not to break it. */
+ * dislike bridging), and I just try not to break it.
+ */
static void add_to_bridge(int fd, const char *if_name, const char *br_name)
{
int ifidx;
err(1, "can't add %s to bridge %s", if_name, br_name);
}
-/* This sets up the Host end of the network device with an IP address, brings
+/*
+ * This sets up the Host end of the network device with an IP address, brings
* it up so packets will flow, the copies the MAC address into the hwaddr
- * pointer. */
+ * pointer.
+ */
static void configure_device(int fd, const char *tapif, u32 ipaddr)
{
struct ifreq ifr;
/* Start with this zeroed. Messy but sure. */
memset(&ifr, 0, sizeof(ifr));
- /* We open the /dev/net/tun device and tell it we want a tap device. A
+ /*
+ * We open the /dev/net/tun device and tell it we want a tap device. A
* tap device is like a tun device, only somehow different. To tell
* the truth, I completely blundered my way through this code, but it
- * works now! */
+ * works now!
+ */
netfd = open_or_die("/dev/net/tun", O_RDWR);
ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
strcpy(ifr.ifr_name, "tap%d");
TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0)
err(1, "Could not set features for tun device");
- /* We don't need checksums calculated for packets coming in this
- * device: trust us! */
+ /*
+ * We don't need checksums calculated for packets coming in this
+ * device: trust us!
+ */
ioctl(netfd, TUNSETNOCSUM, 1);
memcpy(tapif, ifr.ifr_name, IFNAMSIZ);
return netfd;
}
-/*L:195 Our network is a Host<->Guest network. This can either use bridging or
+/*L:195
+ * Our network is a Host<->Guest network. This can either use bridging or
* routing, but the principle is the same: it uses the "tun" device to inject
* packets into the Host as if they came in from a normal network card. We
- * just shunt packets between the Guest and the tun device. */
+ * just shunt packets between the Guest and the tun device.
+ */
static void setup_tun_net(char *arg)
{
struct device *dev;
dev = new_device("net", VIRTIO_ID_NET);
dev->priv = net_info;
- /* Network devices need a receive and a send queue, just like
- * console. */
+ /* Network devices need a recv and a send queue, just like console. */
add_virtqueue(dev, VIRTQUEUE_NUM, net_input);
add_virtqueue(dev, VIRTQUEUE_NUM, net_output);
- /* We need a socket to perform the magic network ioctls to bring up the
- * tap interface, connect to the bridge etc. Any socket will do! */
+ /*
+ * We need a socket to perform the magic network ioctls to bring up the
+ * tap interface, connect to the bridge etc. Any socket will do!
+ */
ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
if (ipfd < 0)
err(1, "opening IP socket");
devices.device_num, tapif, arg);
}
-/* Our block (disk) device should be really simple: the Guest asks for a block
+/*
+ * Our block (disk) device should be really simple: the Guest asks for a block
* number and we read or write that position in the file. Unfortunately, that
* was amazingly slow: the Guest waits until the read is finished before
* running anything else, even if it could have been doing useful work.
* We could use async I/O, except it's reputed to suck so hard that characters
* actually go missing from your code when you try to use it.
*
- * So we farm the I/O out to thread, and communicate with it via a pipe. */
+ * So this was one reason why lguest now does all virtqueue servicing in
+ * separate threads: it's more efficient and more like a real device.
+ */
/* This hangs off device->priv. */
struct vblk_info
/* Get the next request. */
head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
- /* Every block request should contain at least one output buffer
+ /*
+ * Every block request should contain at least one output buffer
* (detailing the location on disk and the type of request) and one
- * input buffer (to hold the result). */
+ * input buffer (to hold the result).
+ */
if (out_num == 0 || in_num == 0)
errx(1, "Bad virtblk cmd %u out=%u in=%u",
head, out_num, in_num);
in = convert(&iov[out_num+in_num-1], u8);
off = out->sector * 512;
- /* The block device implements "barriers", where the Guest indicates
+ /*
+ * The block device implements "barriers", where the Guest indicates
* that it wants all previous writes to occur before this write. We
* don't have a way of asking our kernel to do a barrier, so we just
- * synchronize all the data in the file. Pretty poor, no? */
+ * synchronize all the data in the file. Pretty poor, no?
+ */
if (out->type & VIRTIO_BLK_T_BARRIER)
fdatasync(vblk->fd);
- /* In general the virtio block driver is allowed to try SCSI commands.
- * It'd be nice if we supported eject, for example, but we don't. */
+ /*
+ * In general the virtio block driver is allowed to try SCSI commands.
+ * It'd be nice if we supported eject, for example, but we don't.
+ */
if (out->type & VIRTIO_BLK_T_SCSI_CMD) {
fprintf(stderr, "Scsi commands unsupported\n");
*in = VIRTIO_BLK_S_UNSUPP;
wlen = sizeof(*in);
} else if (out->type & VIRTIO_BLK_T_OUT) {
- /* Write */
-
- /* Move to the right location in the block file. This can fail
- * if they try to write past end. */
+ /*
+ * Write
+ *
+ * Move to the right location in the block file. This can fail
+ * if they try to write past end.
+ */
if (lseek64(vblk->fd, off, SEEK_SET) != off)
err(1, "Bad seek to sector %llu", out->sector);
ret = writev(vblk->fd, iov+1, out_num-1);
verbose("WRITE to sector %llu: %i\n", out->sector, ret);
- /* Grr... Now we know how long the descriptor they sent was, we
+ /*
+ * Grr... Now we know how long the descriptor they sent was, we
* make sure they didn't try to write over the end of the block
- * file (possibly extending it). */
+ * file (possibly extending it).
+ */
if (ret > 0 && off + ret > vblk->len) {
/* Trim it back to the correct length */
ftruncate64(vblk->fd, vblk->len);
wlen = sizeof(*in);
*in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
} else {
- /* Read */
-
- /* Move to the right location in the block file. This can fail
- * if they try to read past end. */
+ /*
+ * Read
+ *
+ * Move to the right location in the block file. This can fail
+ * if they try to read past end.
+ */
if (lseek64(vblk->fd, off, SEEK_SET) != off)
err(1, "Bad seek to sector %llu", out->sector);
}
}
- /* OK, so we noted that it was pretty poor to use an fdatasync as a
+ /*
+ * OK, so we noted that it was pretty poor to use an fdatasync as a
* barrier. But Christoph Hellwig points out that we need a sync
* *afterwards* as well: "Barriers specify no reordering to the front
- * or the back." And Jens Axboe confirmed it, so here we are: */
+ * or the back." And Jens Axboe confirmed it, so here we are:
+ */
if (out->type & VIRTIO_BLK_T_BARRIER)
fdatasync(vblk->fd);
struct vblk_info *vblk;
struct virtio_blk_config conf;
- /* The device responds to return from I/O thread. */
+ /* Creat the device. */
dev = new_device("block", VIRTIO_ID_BLOCK);
/* The device has one virtqueue, where the Guest places requests. */
/* Tell Guest how many sectors this device has. */
conf.capacity = cpu_to_le64(vblk->len / 512);
- /* Tell Guest not to put in too many descriptors at once: two are used
- * for the in and out elements. */
+ /*
+ * Tell Guest not to put in too many descriptors at once: two are used
+ * for the in and out elements.
+ */
add_feature(dev, VIRTIO_BLK_F_SEG_MAX);
conf.seg_max = cpu_to_le32(VIRTQUEUE_NUM - 2);
++devices.device_num, le64_to_cpu(conf.capacity));
}
-struct rng_info {
- int rfd;
-};
-
-/* Our random number generator device reads from /dev/random into the Guest's
+/*L:211
+ * Our random number generator device reads from /dev/random into the Guest's
* input buffers. The usual case is that the Guest doesn't want random numbers
* and so has no buffers although /dev/random is still readable, whereas
* console is the reverse.
*
- * The same logic applies, however. */
+ * The same logic applies, however.
+ */
+struct rng_info {
+ int rfd;
+};
+
static void rng_input(struct virtqueue *vq)
{
int len;
if (out_num)
errx(1, "Output buffers in rng?");
- /* This is why we convert to iovecs: the readv() call uses them, and so
+ /*
+ * This is why we convert to iovecs: the readv() call uses them, and so
* it reads straight into the Guest's buffer. We loop to make sure we
- * fill it. */
+ * fill it.
+ */
while (!iov_empty(iov, in_num)) {
len = readv(rng_info->rfd, iov, in_num);
if (len <= 0)
add_used(vq, head, totlen);
}
-/* And this creates a "hardware" random number device for the Guest. */
+/*L:199
+ * This creates a "hardware" random number device for the Guest.
+ */
static void setup_rng(void)
{
struct device *dev;
struct rng_info *rng_info = malloc(sizeof(*rng_info));
+ /* Our device's privat info simply contains the /dev/random fd. */
rng_info->rfd = open_or_die("/dev/random", O_RDONLY);
- /* The device responds to return from I/O thread. */
+ /* Create the new device. */
dev = new_device("rng", VIRTIO_ID_RNG);
dev->priv = rng_info;
{
unsigned int i;
- /* Since we don't track all open fds, we simply close everything beyond
- * stderr. */
+ /*
+ * Since we don't track all open fds, we simply close everything beyond
+ * stderr.
+ */
for (i = 3; i < FD_SETSIZE; i++)
close(i);
err(1, "Could not exec %s", main_args[0]);
}
-/*L:220 Finally we reach the core of the Launcher which runs the Guest, serves
- * its input and output, and finally, lays it to rest. */
+/*L:220
+ * Finally we reach the core of the Launcher which runs the Guest, serves
+ * its input and output, and finally, lays it to rest.
+ */
static void __attribute__((noreturn)) run_guest(void)
{
for (;;) {
*
* Are you ready? Take a deep breath and join me in the core of the Host, in
* "make Host".
- :*/
+:*/
static struct option opts[] = {
{ "verbose", 0, NULL, 'v' },
/*L:105 The main routine is where the real work begins: */
int main(int argc, char *argv[])
{
- /* Memory, top-level pagetable, code startpoint and size of the
- * (optional) initrd. */
+ /* Memory, code startpoint and size of the (optional) initrd. */
unsigned long mem = 0, start, initrd_size = 0;
/* Two temporaries. */
int i, c;
/* Save the args: we "reboot" by execing ourselves again. */
main_args = argv;
- /* First we initialize the device list. We keep a pointer to the last
+ /*
+ * First we initialize the device list. We keep a pointer to the last
* device, and the next interrupt number to use for devices (1:
- * remember that 0 is used by the timer). */
+ * remember that 0 is used by the timer).
+ */
devices.lastdev = NULL;
devices.next_irq = 1;
cpu_id = 0;
- /* We need to know how much memory so we can set up the device
+ /*
+ * We need to know how much memory so we can set up the device
* descriptor and memory pages for the devices as we parse the command
* line. So we quickly look through the arguments to find the amount
- * of memory now. */
+ * of memory now.
+ */
for (i = 1; i < argc; i++) {
if (argv[i][0] != '-') {
mem = atoi(argv[i]) * 1024 * 1024;
- /* We start by mapping anonymous pages over all of
+ /*
+ * We start by mapping anonymous pages over all of
* guest-physical memory range. This fills it with 0,
* and ensures that the Guest won't be killed when it
- * tries to access it. */
+ * tries to access it.
+ */
guest_base = map_zeroed_pages(mem / getpagesize()
+ DEVICE_PAGES);
guest_limit = mem;
usage();
}
}
- /* After the other arguments we expect memory and kernel image name,
- * followed by command line arguments for the kernel. */
+ /*
+ * After the other arguments we expect memory and kernel image name,
+ * followed by command line arguments for the kernel.
+ */
if (optind + 2 > argc)
usage();
/* Map the initrd image if requested (at top of physical memory) */
if (initrd_name) {
initrd_size = load_initrd(initrd_name, mem);
- /* These are the location in the Linux boot header where the
- * start and size of the initrd are expected to be found. */
+ /*
+ * These are the location in the Linux boot header where the
+ * start and size of the initrd are expected to be found.
+ */
boot->hdr.ramdisk_image = mem - initrd_size;
boot->hdr.ramdisk_size = initrd_size;
/* The bootloader type 0xFF means "unknown"; that's OK. */
boot->hdr.type_of_loader = 0xFF;
}
- /* The Linux boot header contains an "E820" memory map: ours is a
- * simple, single region. */
+ /*
+ * The Linux boot header contains an "E820" memory map: ours is a
+ * simple, single region.
+ */
boot->e820_entries = 1;
boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM });
- /* The boot header contains a command line pointer: we put the command
- * line after the boot header. */
+ /*
+ * The boot header contains a command line pointer: we put the command
+ * line after the boot header.
+ */
boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1);
/* We use a simple helper to copy the arguments separated by spaces. */
concat((char *)(boot + 1), argv+optind+2);
/* Tell the entry path not to try to reload segment registers. */
boot->hdr.loadflags |= KEEP_SEGMENTS;
- /* We tell the kernel to initialize the Guest: this returns the open
- * /dev/lguest file descriptor. */
+ /*
+ * We tell the kernel to initialize the Guest: this returns the open
+ * /dev/lguest file descriptor.
+ */
tell_kernel(start);
/* Ensure that we terminate if a child dies. */
/* Pages for switcher itself, then two pages per cpu */
#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * nr_cpu_ids)
-/* We map at -4M (-2M when PAE is activated) for ease of mapping
- * into the guest (one PTE page). */
+/* We map at -4M (-2M for PAE) for ease of mapping (one PTE page). */
#ifdef CONFIG_X86_PAE
#define SWITCHER_ADDR 0xFFE00000
#else
#include <asm/hw_irq.h>
#include <asm/kvm_para.h>
-/*G:030 But first, how does our Guest contact the Host to ask for privileged
+/*G:030
+ * But first, how does our Guest contact the Host to ask for privileged
* operations? There are two ways: the direct way is to make a "hypercall",
* to make requests of the Host Itself.
*
*
* Grossly invalid calls result in Sudden Death at the hands of the vengeful
* Host, rather than returning failure. This reflects Winston Churchill's
- * definition of a gentleman: "someone who is only rude intentionally". */
-/*:*/
+ * definition of a gentleman: "someone who is only rude intentionally".
+:*/
/* Can't use our min() macro here: needs to be a constant */
#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)
#define LHCALL_RING_SIZE 64
struct hcall_args {
- /* These map directly onto eax, ebx, ecx, edx and esi
- * in struct lguest_regs */
+ /* These map directly onto eax/ebx/ecx/edx/esi in struct lguest_regs */
unsigned long arg0, arg1, arg2, arg3, arg4;
};
*
* So how does the kernel know it's a Guest? We'll see that later, but let's
* just say that we end up here where we replace the native functions various
- * "paravirt" structures with our Guest versions, then boot like normal. :*/
+ * "paravirt" structures with our Guest versions, then boot like normal.
+:*/
/*
* Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation.
*
* The Guest in our tale is a simple creature: identical to the Host but
* behaving in simplified but equivalent ways. In particular, the Guest is the
- * same kernel as the Host (or at least, built from the same source code). :*/
+ * same kernel as the Host (or at least, built from the same source code).
+:*/
struct lguest_data lguest_data = {
.hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF },
.syscall_vec = SYSCALL_VECTOR,
};
-/*G:037 async_hcall() is pretty simple: I'm quite proud of it really. We have a
+/*G:037
+ * async_hcall() is pretty simple: I'm quite proud of it really. We have a
* ring buffer of stored hypercalls which the Host will run though next time we
* do a normal hypercall. Each entry in the ring has 5 slots for the hypercall
* arguments, and a "hcall_status" word which is 0 if the call is ready to go,
* If we come around to a slot which hasn't been finished, then the table is
* full and we just make the hypercall directly. This has the nice side
* effect of causing the Host to run all the stored calls in the ring buffer
- * which empties it for next time! */
+ * which empties it for next time!
+ */
static void async_hcall(unsigned long call, unsigned long arg1,
unsigned long arg2, unsigned long arg3,
unsigned long arg4)
static unsigned int next_call;
unsigned long flags;
- /* Disable interrupts if not already disabled: we don't want an
+ /*
+ * Disable interrupts if not already disabled: we don't want an
* interrupt handler making a hypercall while we're already doing
- * one! */
+ * one!
+ */
local_irq_save(flags);
if (lguest_data.hcall_status[next_call] != 0xFF) {
/* Table full, so do normal hcall which will flush table. */
local_irq_restore(flags);
}
-/*G:035 Notice the lazy_hcall() above, rather than hcall(). This is our first
- * real optimization trick!
+/*G:035
+ * Notice the lazy_hcall() above, rather than hcall(). This is our first real
+ * optimization trick!
*
* When lazy_mode is set, it means we're allowed to defer all hypercalls and do
* them as a batch when lazy_mode is eventually turned off. Because hypercalls
* lguest_leave_lazy_mode().
*
* So, when we're in lazy mode, we call async_hcall() to store the call for
- * future processing: */
+ * future processing:
+ */
static void lazy_hcall1(unsigned long call,
unsigned long arg1)
{
* check there before it tries to deliver an interrupt.
*/
-/* save_flags() is expected to return the processor state (ie. "flags"). The
+/*
+ * save_flags() is expected to return the processor state (ie. "flags"). The
* flags word contains all kind of stuff, but in practice Linux only cares
- * about the interrupt flag. Our "save_flags()" just returns that. */
+ * about the interrupt flag. Our "save_flags()" just returns that.
+ */
static unsigned long save_fl(void)
{
return lguest_data.irq_enabled;
lguest_data.irq_enabled = 0;
}
-/* Let's pause a moment. Remember how I said these are called so often?
+/*
+ * Let's pause a moment. Remember how I said these are called so often?
* Jeremy Fitzhardinge optimized them so hard early in 2009 that he had to
* break some rules. In particular, these functions are assumed to save their
* own registers if they need to: normal C functions assume they can trash the
* eax register. To use normal C functions, we use
* PV_CALLEE_SAVE_REGS_THUNK(), which pushes %eax onto the stack, calls the
- * C function, then restores it. */
+ * C function, then restores it.
+ */
PV_CALLEE_SAVE_REGS_THUNK(save_fl);
PV_CALLEE_SAVE_REGS_THUNK(irq_disable);
/*:*/
extern void lg_irq_enable(void);
extern void lg_restore_fl(unsigned long flags);
-/*M:003 Note that we don't check for outstanding interrupts when we re-enable
- * them (or when we unmask an interrupt). This seems to work for the moment,
- * since interrupts are rare and we'll just get the interrupt on the next timer
- * tick, but now we can run with CONFIG_NO_HZ, we should revisit this. One way
- * would be to put the "irq_enabled" field in a page by itself, and have the
- * Host write-protect it when an interrupt comes in when irqs are disabled.
- * There will then be a page fault as soon as interrupts are re-enabled.
+/*M:003
+ * Note that we don't check for outstanding interrupts when we re-enable them
+ * (or when we unmask an interrupt). This seems to work for the moment, since
+ * interrupts are rare and we'll just get the interrupt on the next timer tick,
+ * but now we can run with CONFIG_NO_HZ, we should revisit this. One way would
+ * be to put the "irq_enabled" field in a page by itself, and have the Host
+ * write-protect it when an interrupt comes in when irqs are disabled. There
+ * will then be a page fault as soon as interrupts are re-enabled.
*
* A better method is to implement soft interrupt disable generally for x86:
* instead of disabling interrupts, we set a flag. If an interrupt does come
* in, we then disable them for real. This is uncommon, so we could simply use
- * a hypercall for interrupt control and not worry about efficiency. :*/
+ * a hypercall for interrupt control and not worry about efficiency.
+:*/
/*G:034
* The Interrupt Descriptor Table (IDT).
static void lguest_write_idt_entry(gate_desc *dt,
int entrynum, const gate_desc *g)
{
- /* The gate_desc structure is 8 bytes long: we hand it to the Host in
+ /*
+ * The gate_desc structure is 8 bytes long: we hand it to the Host in
* two 32-bit chunks. The whole 32-bit kernel used to hand descriptors
* around like this; typesafety wasn't a big concern in Linux's early
- * years. */
+ * years.
+ */
u32 *desc = (u32 *)g;
/* Keep the local copy up to date. */
native_write_idt_entry(dt, entrynum, g);
kvm_hypercall3(LHCALL_LOAD_IDT_ENTRY, entrynum, desc[0], desc[1]);
}
-/* Changing to a different IDT is very rare: we keep the IDT up-to-date every
+/*
+ * Changing to a different IDT is very rare: we keep the IDT up-to-date every
* time it is written, so we can simply loop through all entries and tell the
- * Host about them. */
+ * Host about them.
+ */
static void lguest_load_idt(const struct desc_ptr *desc)
{
unsigned int i;
kvm_hypercall3(LHCALL_LOAD_GDT_ENTRY, i, gdt[i].a, gdt[i].b);
}
-/* For a single GDT entry which changes, we do the lazy thing: alter our GDT,
+/*
+ * For a single GDT entry which changes, we do the lazy thing: alter our GDT,
* then tell the Host to reload the entire thing. This operation is so rare
- * that this naive implementation is reasonable. */
+ * that this naive implementation is reasonable.
+ */
static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum,
const void *desc, int type)
{
dt[entrynum].a, dt[entrynum].b);
}
-/* OK, I lied. There are three "thread local storage" GDT entries which change
+/*
+ * OK, I lied. There are three "thread local storage" GDT entries which change
* on every context switch (these three entries are how glibc implements
- * __thread variables). So we have a hypercall specifically for this case. */
+ * __thread variables). So we have a hypercall specifically for this case.
+ */
static void lguest_load_tls(struct thread_struct *t, unsigned int cpu)
{
- /* There's one problem which normal hardware doesn't have: the Host
+ /*
+ * There's one problem which normal hardware doesn't have: the Host
* can't handle us removing entries we're currently using. So we clear
- * the GS register here: if it's needed it'll be reloaded anyway. */
+ * the GS register here: if it's needed it'll be reloaded anyway.
+ */
lazy_load_gs(0);
lazy_hcall2(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu);
}
-/*G:038 That's enough excitement for now, back to ploughing through each of
- * the different pv_ops structures (we're about 1/3 of the way through).
+/*G:038
+ * That's enough excitement for now, back to ploughing through each of the
+ * different pv_ops structures (we're about 1/3 of the way through).
*
* This is the Local Descriptor Table, another weird Intel thingy. Linux only
* uses this for some strange applications like Wine. We don't do anything
- * here, so they'll get an informative and friendly Segmentation Fault. */
+ * here, so they'll get an informative and friendly Segmentation Fault.
+ */
static void lguest_set_ldt(const void *addr, unsigned entries)
{
}
-/* This loads a GDT entry into the "Task Register": that entry points to a
+/*
+ * This loads a GDT entry into the "Task Register": that entry points to a
* structure called the Task State Segment. Some comments scattered though the
* kernel code indicate that this used for task switching in ages past, along
* with blood sacrifice and astrology.
* Now there's nothing interesting in here that we don't get told elsewhere.
* But the native version uses the "ltr" instruction, which makes the Host
* complain to the Guest about a Segmentation Fault and it'll oops. So we
- * override the native version with a do-nothing version. */
+ * override the native version with a do-nothing version.
+ */
static void lguest_load_tr_desc(void)
{
}
-/* The "cpuid" instruction is a way of querying both the CPU identity
+/*
+ * The "cpuid" instruction is a way of querying both the CPU identity
* (manufacturer, model, etc) and its features. It was introduced before the
* Pentium in 1993 and keeps getting extended by both Intel, AMD and others.
* As you might imagine, after a decade and a half this treatment, it is now a
* giant ball of hair. Its entry in the current Intel manual runs to 28 pages.
*
* This instruction even it has its own Wikipedia entry. The Wikipedia entry
- * has been translated into 4 languages. I am not making this up!
+ * has been translated into 5 languages. I am not making this up!
*
* We could get funky here and identify ourselves as "GenuineLguest", but
* instead we just use the real "cpuid" instruction. Then I pretty much turned
* Replacing the cpuid so we can turn features off is great for the kernel, but
* anyone (including userspace) can just use the raw "cpuid" instruction and
* the Host won't even notice since it isn't privileged. So we try not to get
- * too worked up about it. */
+ * too worked up about it.
+ */
static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
unsigned int *cx, unsigned int *dx)
{
native_cpuid(ax, bx, cx, dx);
switch (function) {
- case 0: /* ID and highest CPUID. Futureproof a little by sticking to
- * older ones. */
+ /*
+ * CPUID 0 gives the highest legal CPUID number (and the ID string).
+ * We futureproof our code a little by sticking to known CPUID values.
+ */
+ case 0:
if (*ax > 5)
*ax = 5;
break;
- case 1: /* Basic feature request. */
- /* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */
+
+ /*
+ * CPUID 1 is a basic feature request.
+ *
+ * CX: we only allow kernel to see SSE3, CMPXCHG16B and SSSE3
+ * DX: SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU and PAE.
+ */
+ case 1:
*cx &= 0x00002201;
- /* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU, PAE. */
*dx &= 0x07808151;
- /* The Host can do a nice optimization if it knows that the
+ /*
+ * The Host can do a nice optimization if it knows that the
* kernel mappings (addresses above 0xC0000000 or whatever
* PAGE_OFFSET is set to) haven't changed. But Linux calls
* flush_tlb_user() for both user and kernel mappings unless
- * the Page Global Enable (PGE) feature bit is set. */
+ * the Page Global Enable (PGE) feature bit is set.
+ */
*dx |= 0x00002000;
- /* We also lie, and say we're family id 5. 6 or greater
+ /*
+ * We also lie, and say we're family id 5. 6 or greater
* leads to a rdmsr in early_init_intel which we can't handle.
- * Family ID is returned as bits 8-12 in ax. */
+ * Family ID is returned as bits 8-12 in ax.
+ */
*ax &= 0xFFFFF0FF;
*ax |= 0x00000500;
break;
+ /*
+ * 0x80000000 returns the highest Extended Function, so we futureproof
+ * like we do above by limiting it to known fields.
+ */
case 0x80000000:
- /* Futureproof this a little: if they ask how much extended
- * processor information there is, limit it to known fields. */
if (*ax > 0x80000008)
*ax = 0x80000008;
break;
+
+ /*
+ * PAE systems can mark pages as non-executable. Linux calls this the
+ * NX bit. Intel calls it XD (eXecute Disable), AMD EVP (Enhanced
+ * Virus Protection). We just switch turn if off here, since we don't
+ * support it.
+ */
case 0x80000001:
- /* Here we should fix nx cap depending on host. */
- /* For this version of PAE, we just clear NX bit. */
*dx &= ~(1 << 20);
break;
}
}
-/* Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4.
+/*
+ * Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4.
* I assume there's a cr1, but it hasn't bothered us yet, so we'll not bother
* it. The Host needs to know when the Guest wants to change them, so we have
* a whole series of functions like read_cr0() and write_cr0().
* name like "FPUTRAP bit" be a little less cryptic?
*
* We store cr0 locally because the Host never changes it. The Guest sometimes
- * wants to read it and we'd prefer not to bother the Host unnecessarily. */
+ * wants to read it and we'd prefer not to bother the Host unnecessarily.
+ */
static unsigned long current_cr0;
static void lguest_write_cr0(unsigned long val)
{
return current_cr0;
}
-/* Intel provided a special instruction to clear the TS bit for people too cool
+/*
+ * Intel provided a special instruction to clear the TS bit for people too cool
* to use write_cr0() to do it. This "clts" instruction is faster, because all
- * the vowels have been optimized out. */
+ * the vowels have been optimized out.
+ */
static void lguest_clts(void)
{
lazy_hcall1(LHCALL_TS, 0);
current_cr0 &= ~X86_CR0_TS;
}
-/* cr2 is the virtual address of the last page fault, which the Guest only ever
+/*
+ * cr2 is the virtual address of the last page fault, which the Guest only ever
* reads. The Host kindly writes this into our "struct lguest_data", so we
- * just read it out of there. */
+ * just read it out of there.
+ */
static unsigned long lguest_read_cr2(void)
{
return lguest_data.cr2;
/* See lguest_set_pte() below. */
static bool cr3_changed = false;
-/* cr3 is the current toplevel pagetable page: the principle is the same as
+/*
+ * cr3 is the current toplevel pagetable page: the principle is the same as
* cr0. Keep a local copy, and tell the Host when it changes. The only
* difference is that our local copy is in lguest_data because the Host needs
- * to set it upon our initial hypercall. */
+ * to set it upon our initial hypercall.
+ */
static void lguest_write_cr3(unsigned long cr3)
{
lguest_data.pgdir = cr3;
* the real page tables based on the Guests'.
*/
-/* The Guest calls this to set a second-level entry (pte), ie. to map a page
+/*
+ * The Guest calls this to set a second-level entry (pte), ie. to map a page
* into a process' address space. We set the entry then tell the Host the
* toplevel and address this corresponds to. The Guest uses one pagetable per
- * process, so we need to tell the Host which one we're changing (mm->pgd). */
+ * process, so we need to tell the Host which one we're changing (mm->pgd).
+ */
static void lguest_pte_update(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
lguest_pte_update(mm, addr, ptep);
}
-/* The Guest calls lguest_set_pud to set a top-level entry and lguest_set_pmd
+/*
+ * The Guest calls lguest_set_pud to set a top-level entry and lguest_set_pmd
* to set a middle-level entry when PAE is activated.
+ *
* Again, we set the entry then tell the Host which page we changed,
- * and the index of the entry we changed. */
+ * and the index of the entry we changed.
+ */
#ifdef CONFIG_X86_PAE
static void lguest_set_pud(pud_t *pudp, pud_t pudval)
{
}
#else
-/* The Guest calls lguest_set_pmd to set a top-level entry when PAE is not
- * activated. */
+/* The Guest calls lguest_set_pmd to set a top-level entry when !PAE. */
static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
{
native_set_pmd(pmdp, pmdval);
}
#endif
-/* There are a couple of legacy places where the kernel sets a PTE, but we
+/*
+ * There are a couple of legacy places where the kernel sets a PTE, but we
* don't know the top level any more. This is useless for us, since we don't
* know which pagetable is changing or what address, so we just tell the Host
* to forget all of them. Fortunately, this is very rare.
* ... except in early boot when the kernel sets up the initial pagetables,
* which makes booting astonishingly slow: 1.83 seconds! So we don't even tell
* the Host anything changed until we've done the first page table switch,
- * which brings boot back to 0.25 seconds. */
+ * which brings boot back to 0.25 seconds.
+ */
static void lguest_set_pte(pte_t *ptep, pte_t pteval)
{
native_set_pte(ptep, pteval);
}
#endif
-/* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
+/*
+ * Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
* native page table operations. On native hardware you can set a new page
* table entry whenever you want, but if you want to remove one you have to do
* a TLB flush (a TLB is a little cache of page table entries kept by the CPU).
* called when a valid entry is written, not when it's removed (ie. marked not
* present). Instead, this is where we come when the Guest wants to remove a
* page table entry: we tell the Host to set that entry to 0 (ie. the present
- * bit is zero). */
+ * bit is zero).
+ */
static void lguest_flush_tlb_single(unsigned long addr)
{
/* Simply set it to zero: if it was not, it will fault back in. */
lazy_hcall3(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
}
-/* This is what happens after the Guest has removed a large number of entries.
+/*
+ * This is what happens after the Guest has removed a large number of entries.
* This tells the Host that any of the page table entries for userspace might
- * have changed, ie. virtual addresses below PAGE_OFFSET. */
+ * have changed, ie. virtual addresses below PAGE_OFFSET.
+ */
static void lguest_flush_tlb_user(void)
{
lazy_hcall1(LHCALL_FLUSH_TLB, 0);
}
-/* This is called when the kernel page tables have changed. That's not very
+/*
+ * This is called when the kernel page tables have changed. That's not very
* common (unless the Guest is using highmem, which makes the Guest extremely
- * slow), so it's worth separating this from the user flushing above. */
+ * slow), so it's worth separating this from the user flushing above.
+ */
static void lguest_flush_tlb_kernel(void)
{
lazy_hcall1(LHCALL_FLUSH_TLB, 1);
.unmask = enable_lguest_irq,
};
-/* This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
+/*
+ * This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
* interrupt (except 128, which is used for system calls), and then tells the
* Linux infrastructure that each interrupt is controlled by our level-based
- * lguest interrupt controller. */
+ * lguest interrupt controller.
+ */
static void __init lguest_init_IRQ(void)
{
unsigned int i;
for (i = FIRST_EXTERNAL_VECTOR; i < NR_VECTORS; i++) {
- /* Some systems map "vectors" to interrupts weirdly. Lguest has
- * a straightforward 1 to 1 mapping, so force that here. */
+ /* Some systems map "vectors" to interrupts weirdly. Not us! */
__get_cpu_var(vector_irq)[i] = i - FIRST_EXTERNAL_VECTOR;
if (i != SYSCALL_VECTOR)
set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
}
- /* This call is required to set up for 4k stacks, where we have
- * separate stacks for hard and soft interrupts. */
+
+ /*
+ * This call is required to set up for 4k stacks, where we have
+ * separate stacks for hard and soft interrupts.
+ */
irq_ctx_init(smp_processor_id());
}
return lguest_data.time.tv_sec;
}
-/* The TSC is an Intel thing called the Time Stamp Counter. The Host tells us
+/*
+ * The TSC is an Intel thing called the Time Stamp Counter. The Host tells us
* what speed it runs at, or 0 if it's unusable as a reliable clock source.
* This matches what we want here: if we return 0 from this function, the x86
- * TSC clock will give up and not register itself. */
+ * TSC clock will give up and not register itself.
+ */
static unsigned long lguest_tsc_khz(void)
{
return lguest_data.tsc_khz;
}
-/* If we can't use the TSC, the kernel falls back to our lower-priority
- * "lguest_clock", where we read the time value given to us by the Host. */
+/*
+ * If we can't use the TSC, the kernel falls back to our lower-priority
+ * "lguest_clock", where we read the time value given to us by the Host.
+ */
static cycle_t lguest_clock_read(struct clocksource *cs)
{
unsigned long sec, nsec;
- /* Since the time is in two parts (seconds and nanoseconds), we risk
+ /*
+ * Since the time is in two parts (seconds and nanoseconds), we risk
* reading it just as it's changing from 99 & 0.999999999 to 100 and 0,
* and getting 99 and 0. As Linux tends to come apart under the stress
- * of time travel, we must be careful: */
+ * of time travel, we must be careful:
+ */
do {
/* First we read the seconds part. */
sec = lguest_data.time.tv_sec;
- /* This read memory barrier tells the compiler and the CPU that
+ /*
+ * This read memory barrier tells the compiler and the CPU that
* this can't be reordered: we have to complete the above
- * before going on. */
+ * before going on.
+ */
rmb();
/* Now we read the nanoseconds part. */
nsec = lguest_data.time.tv_nsec;
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
-/* We also need a "struct clock_event_device": Linux asks us to set it to go
+/*
+ * We also need a "struct clock_event_device": Linux asks us to set it to go
* off some time in the future. Actually, James Morris figured all this out, I
- * just applied the patch. */
+ * just applied the patch.
+ */
static int lguest_clockevent_set_next_event(unsigned long delta,
struct clock_event_device *evt)
{
.max_delta_ns = LG_CLOCK_MAX_DELTA,
};
-/* This is the Guest timer interrupt handler (hardware interrupt 0). We just
- * call the clockevent infrastructure and it does whatever needs doing. */
+/*
+ * This is the Guest timer interrupt handler (hardware interrupt 0). We just
+ * call the clockevent infrastructure and it does whatever needs doing.
+ */
static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
{
unsigned long flags;
local_irq_restore(flags);
}
-/* At some point in the boot process, we get asked to set up our timing
+/*
+ * At some point in the boot process, we get asked to set up our timing
* infrastructure. The kernel doesn't expect timer interrupts before this, but
* we cleverly initialized the "blocked_interrupts" field of "struct
- * lguest_data" so that timer interrupts were blocked until now. */
+ * lguest_data" so that timer interrupts were blocked until now.
+ */
static void lguest_time_init(void)
{
/* Set up the timer interrupt (0) to go to our simple timer routine */
* to work. They're pretty simple.
*/
-/* The Guest needs to tell the Host what stack it expects traps to use. For
+/*
+ * The Guest needs to tell the Host what stack it expects traps to use. For
* native hardware, this is part of the Task State Segment mentioned above in
* lguest_load_tr_desc(), but to help hypervisors there's this special call.
*
* We tell the Host the segment we want to use (__KERNEL_DS is the kernel data
* segment), the privilege level (we're privilege level 1, the Host is 0 and
* will not tolerate us trying to use that), the stack pointer, and the number
- * of pages in the stack. */
+ * of pages in the stack.
+ */
static void lguest_load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
{
/* FIXME: Implement */
}
-/* There are times when the kernel wants to make sure that no memory writes are
+/*
+ * There are times when the kernel wants to make sure that no memory writes are
* caught in the cache (that they've all reached real hardware devices). This
* doesn't matter for the Guest which has virtual hardware.
*
{
}
-/* If the Guest expects to have an Advanced Programmable Interrupt Controller,
+/*
+ * If the Guest expects to have an Advanced Programmable Interrupt Controller,
* we play dumb by ignoring writes and returning 0 for reads. So it's no
* longer Programmable nor Controlling anything, and I don't think 8 lines of
* code qualifies for Advanced. It will also never interrupt anything. It
- * does, however, allow us to get through the Linux boot code. */
+ * does, however, allow us to get through the Linux boot code.
+ */
#ifdef CONFIG_X86_LOCAL_APIC
static void lguest_apic_write(u32 reg, u32 v)
{
kvm_hypercall0(LHCALL_HALT);
}
-/* The SHUTDOWN hypercall takes a string to describe what's happening, and
+/*
+ * The SHUTDOWN hypercall takes a string to describe what's happening, and
* an argument which says whether this to restart (reboot) the Guest or not.
*
* Note that the Host always prefers that the Guest speak in physical addresses
- * rather than virtual addresses, so we use __pa() here. */
+ * rather than virtual addresses, so we use __pa() here.
+ */
static void lguest_power_off(void)
{
kvm_hypercall2(LHCALL_SHUTDOWN, __pa("Power down"),
* nice to move it back to lguest_init. Patch welcome... */
atomic_notifier_chain_register(&panic_notifier_list, &paniced);
- /* The Linux bootloader header contains an "e820" memory map: the
- * Launcher populated the first entry with our memory limit. */
+ /*
+ *The Linux bootloader header contains an "e820" memory map: the
+ * Launcher populated the first entry with our memory limit.
+ */
e820_add_region(boot_params.e820_map[0].addr,
boot_params.e820_map[0].size,
boot_params.e820_map[0].type);
return "LGUEST";
}
-/* We will eventually use the virtio console device to produce console output,
+/*
+ * We will eventually use the virtio console device to produce console output,
* but before that is set up we use LHCALL_NOTIFY on normal memory to produce
- * console output. */
+ * console output.
+ */
static __init int early_put_chars(u32 vtermno, const char *buf, int count)
{
char scratch[17];
unsigned int len = count;
- /* We use a nul-terminated string, so we have to make a copy. Icky,
- * huh? */
+ /* We use a nul-terminated string, so we make a copy. Icky, huh? */
if (len > sizeof(scratch) - 1)
len = sizeof(scratch) - 1;
scratch[len] = '\0';
return len;
}
-/* Rebooting also tells the Host we're finished, but the RESTART flag tells the
- * Launcher to reboot us. */
+/*
+ * Rebooting also tells the Host we're finished, but the RESTART flag tells the
+ * Launcher to reboot us.
+ */
static void lguest_restart(char *reason)
{
kvm_hypercall2(LHCALL_SHUTDOWN, __pa(reason), LGUEST_SHUTDOWN_RESTART);
* fit comfortably.
*
* First we need assembly templates of each of the patchable Guest operations,
- * and these are in i386_head.S. */
+ * and these are in i386_head.S.
+ */
/*G:060 We construct a table from the assembler templates: */
static const struct lguest_insns
[PARAVIRT_PATCH(pv_irq_ops.save_fl)] = { lgstart_pushf, lgend_pushf },
};
-/* Now our patch routine is fairly simple (based on the native one in
+/*
+ * Now our patch routine is fairly simple (based on the native one in
* paravirt.c). If we have a replacement, we copy it in and return how much of
- * the available space we used. */
+ * the available space we used.
+ */
static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
unsigned long addr, unsigned len)
{
insn_len = lguest_insns[type].end - lguest_insns[type].start;
- /* Similarly if we can't fit replacement (shouldn't happen, but let's
- * be thorough). */
+ /* Similarly if it can't fit (doesn't happen, but let's be thorough). */
if (len < insn_len)
return paravirt_patch_default(type, clobber, ibuf, addr, len);
return insn_len;
}
-/*G:029 Once we get to lguest_init(), we know we're a Guest. The various
+/*G:029
+ * Once we get to lguest_init(), we know we're a Guest. The various
* pv_ops structures in the kernel provide points for (almost) every routine we
- * have to override to avoid privileged instructions. */
+ * have to override to avoid privileged instructions.
+ */
__init void lguest_init(void)
{
- /* We're under lguest, paravirt is enabled, and we're running at
- * privilege level 1, not 0 as normal. */
+ /* We're under lguest. */
pv_info.name = "lguest";
+ /* Paravirt is enabled. */
pv_info.paravirt_enabled = 1;
+ /* We're running at privilege level 1, not 0 as normal. */
pv_info.kernel_rpl = 1;
+ /* Everyone except Xen runs with this set. */
pv_info.shared_kernel_pmd = 1;
- /* We set up all the lguest overrides for sensitive operations. These
- * are detailed with the operations themselves. */
+ /*
+ * We set up all the lguest overrides for sensitive operations. These
+ * are detailed with the operations themselves.
+ */
- /* interrupt-related operations */
+ /* Interrupt-related operations */
pv_irq_ops.init_IRQ = lguest_init_IRQ;
pv_irq_ops.save_fl = PV_CALLEE_SAVE(save_fl);
pv_irq_ops.restore_fl = __PV_IS_CALLEE_SAVE(lg_restore_fl);
pv_irq_ops.irq_enable = __PV_IS_CALLEE_SAVE(lg_irq_enable);
pv_irq_ops.safe_halt = lguest_safe_halt;
- /* init-time operations */
+ /* Setup operations */
pv_init_ops.memory_setup = lguest_memory_setup;
pv_init_ops.patch = lguest_patch;
- /* Intercepts of various cpu instructions */
+ /* Intercepts of various CPU instructions */
pv_cpu_ops.load_gdt = lguest_load_gdt;
pv_cpu_ops.cpuid = lguest_cpuid;
pv_cpu_ops.load_idt = lguest_load_idt;
pv_cpu_ops.start_context_switch = paravirt_start_context_switch;
pv_cpu_ops.end_context_switch = lguest_end_context_switch;
- /* pagetable management */
+ /* Pagetable management */
pv_mmu_ops.write_cr3 = lguest_write_cr3;
pv_mmu_ops.flush_tlb_user = lguest_flush_tlb_user;
pv_mmu_ops.flush_tlb_single = lguest_flush_tlb_single;
pv_mmu_ops.pte_update_defer = lguest_pte_update;
#ifdef CONFIG_X86_LOCAL_APIC
- /* apic read/write intercepts */
+ /* APIC read/write intercepts */
set_lguest_basic_apic_ops();
#endif
- /* time operations */
+ /* Time operations */
pv_time_ops.get_wallclock = lguest_get_wallclock;
pv_time_ops.time_init = lguest_time_init;
pv_time_ops.get_tsc_khz = lguest_tsc_khz;
- /* Now is a good time to look at the implementations of these functions
- * before returning to the rest of lguest_init(). */
+ /*
+ * Now is a good time to look at the implementations of these functions
+ * before returning to the rest of lguest_init().
+ */
- /*G:070 Now we've seen all the paravirt_ops, we return to
+ /*G:070
+ * Now we've seen all the paravirt_ops, we return to
* lguest_init() where the rest of the fairly chaotic boot setup
- * occurs. */
+ * occurs.
+ */
- /* The stack protector is a weird thing where gcc places a canary
+ /*
+ * The stack protector is a weird thing where gcc places a canary
* value on the stack and then checks it on return. This file is
* compiled with -fno-stack-protector it, so we got this far without
* problems. The value of the canary is kept at offset 20 from the
* %gs register, so we need to set that up before calling C functions
- * in other files. */
+ * in other files.
+ */
setup_stack_canary_segment(0);
- /* We could just call load_stack_canary_segment(), but we might as
- * call switch_to_new_gdt() which loads the whole table and sets up
- * the per-cpu segment descriptor register %fs as well. */
+
+ /*
+ * We could just call load_stack_canary_segment(), but we might as well
+ * call switch_to_new_gdt() which loads the whole table and sets up the
+ * per-cpu segment descriptor register %fs as well.
+ */
switch_to_new_gdt(0);
/* As described in head_32.S, we map the first 128M of memory. */
max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
- /* The Host<->Guest Switcher lives at the top of our address space, and
+ /*
+ * The Host<->Guest Switcher lives at the top of our address space, and
* the Host told us how big it is when we made LGUEST_INIT hypercall:
- * it put the answer in lguest_data.reserve_mem */
+ * it put the answer in lguest_data.reserve_mem
+ */
reserve_top_address(lguest_data.reserve_mem);
- /* If we don't initialize the lock dependency checker now, it crashes
- * paravirt_disable_iospace. */
+ /*
+ * If we don't initialize the lock dependency checker now, it crashes
+ * paravirt_disable_iospace.
+ */
lockdep_init();
- /* The IDE code spends about 3 seconds probing for disks: if we reserve
+ /*
+ * The IDE code spends about 3 seconds probing for disks: if we reserve
* all the I/O ports up front it can't get them and so doesn't probe.
* Other device drivers are similar (but less severe). This cuts the
- * kernel boot time on my machine from 4.1 seconds to 0.45 seconds. */
+ * kernel boot time on my machine from 4.1 seconds to 0.45 seconds.
+ */
paravirt_disable_iospace();
- /* This is messy CPU setup stuff which the native boot code does before
- * start_kernel, so we have to do, too: */
+ /*
+ * This is messy CPU setup stuff which the native boot code does before
+ * start_kernel, so we have to do, too:
+ */
cpu_detect(&new_cpu_data);
/* head.S usually sets up the first capability word, so do it here. */
new_cpu_data.x86_capability[0] = cpuid_edx(1);
acpi_ht = 0;
#endif
- /* We set the preferred console to "hvc". This is the "hypervisor
+ /*
+ * We set the preferred console to "hvc". This is the "hypervisor
* virtual console" driver written by the PowerPC people, which we also
- * adapted for lguest's use. */
+ * adapted for lguest's use.
+ */
add_preferred_console("hvc", 0, NULL);
/* Register our very early console. */
virtio_cons_early_init(early_put_chars);
- /* Last of all, we set the power management poweroff hook to point to
+ /*
+ * Last of all, we set the power management poweroff hook to point to
* the Guest routine to power off, and the reboot hook to our restart
- * routine. */
+ * routine.
+ */
pm_power_off = lguest_power_off;
machine_ops.restart = lguest_restart;
- /* Now we're set up, call i386_start_kernel() in head32.c and we proceed
- * to boot as normal. It never returns. */
+ /*
+ * Now we're set up, call i386_start_kernel() in head32.c and we proceed
+ * to boot as normal. It never returns.
+ */
i386_start_kernel();
}
/*
#include <asm/thread_info.h>
#include <asm/processor-flags.h>
-/*G:020 Our story starts with the kernel booting into startup_32 in
+/*G:020
+ * Our story starts with the kernel booting into startup_32 in
* arch/x86/kernel/head_32.S. It expects a boot header, which is created by
* the bootloader (the Launcher in our case).
*
* data without remembering to subtract __PAGE_OFFSET!
*
* The .section line puts this code in .init.text so it will be discarded after
- * boot. */
+ * boot.
+ */
.section .init.text, "ax", @progbits
ENTRY(lguest_entry)
- /* We make the "initialization" hypercall now to tell the Host about
- * us, and also find out where it put our page tables. */
+ /*
+ * We make the "initialization" hypercall now to tell the Host about
+ * us, and also find out where it put our page tables.
+ */
movl $LHCALL_LGUEST_INIT, %eax
movl $lguest_data - __PAGE_OFFSET, %ebx
.byte 0x0f,0x01,0xc1 /* KVM_HYPERCALL */
/* Set up the initial stack so we can run C code. */
movl $(init_thread_union+THREAD_SIZE),%esp
- /* Jumps are relative, and we're running __PAGE_OFFSET too low at the
- * moment. */
+ /* Jumps are relative: we're running __PAGE_OFFSET too low. */
jmp lguest_init+__PAGE_OFFSET
-/*G:055 We create a macro which puts the assembler code between lgstart_ and
- * lgend_ markers. These templates are put in the .text section: they can't be
- * discarded after boot as we may need to patch modules, too. */
+/*G:055
+ * We create a macro which puts the assembler code between lgstart_ and lgend_
+ * markers. These templates are put in the .text section: they can't be
+ * discarded after boot as we may need to patch modules, too.
+ */
.text
#define LGUEST_PATCH(name, insns...) \
lgstart_##name: insns; lgend_##name:; \
LGUEST_PATCH(cli, movl $0, lguest_data+LGUEST_DATA_irq_enabled)
LGUEST_PATCH(pushf, movl lguest_data+LGUEST_DATA_irq_enabled, %eax)
-/*G:033 But using those wrappers is inefficient (we'll see why that doesn't
- * matter for save_fl and irq_disable later). If we write our routines
- * carefully in assembler, we can avoid clobbering any registers and avoid
- * jumping through the wrapper functions.
+/*G:033
+ * But using those wrappers is inefficient (we'll see why that doesn't matter
+ * for save_fl and irq_disable later). If we write our routines carefully in
+ * assembler, we can avoid clobbering any registers and avoid jumping through
+ * the wrapper functions.
*
* I skipped over our first piece of assembler, but this one is worth studying
- * in a bit more detail so I'll describe in easy stages. First, the routine
- * to enable interrupts: */
+ * in a bit more detail so I'll describe in easy stages. First, the routine to
+ * enable interrupts:
+ */
ENTRY(lg_irq_enable)
- /* The reverse of irq_disable, this sets lguest_data.irq_enabled to
- * X86_EFLAGS_IF (ie. "Interrupts enabled"). */
+ /*
+ * The reverse of irq_disable, this sets lguest_data.irq_enabled to
+ * X86_EFLAGS_IF (ie. "Interrupts enabled").
+ */
movl $X86_EFLAGS_IF, lguest_data+LGUEST_DATA_irq_enabled
- /* But now we need to check if the Host wants to know: there might have
+ /*
+ * But now we need to check if the Host wants to know: there might have
* been interrupts waiting to be delivered, in which case it will have
* set lguest_data.irq_pending to X86_EFLAGS_IF. If it's not zero, we
- * jump to send_interrupts, otherwise we're done. */
+ * jump to send_interrupts, otherwise we're done.
+ */
testl $0, lguest_data+LGUEST_DATA_irq_pending
jnz send_interrupts
- /* One cool thing about x86 is that you can do many things without using
+ /*
+ * One cool thing about x86 is that you can do many things without using
* a register. In this case, the normal path hasn't needed to save or
- * restore any registers at all! */
+ * restore any registers at all!
+ */
ret
send_interrupts:
- /* OK, now we need a register: eax is used for the hypercall number,
+ /*
+ * OK, now we need a register: eax is used for the hypercall number,
* which is LHCALL_SEND_INTERRUPTS.
*
* We used not to bother with this pending detection at all, which was
* much simpler. Sooner or later the Host would realize it had to
* send us an interrupt. But that turns out to make performance 7
* times worse on a simple tcp benchmark. So now we do this the hard
- * way. */
+ * way.
+ */
pushl %eax
movl $LHCALL_SEND_INTERRUPTS, %eax
- /* This is a vmcall instruction (same thing that KVM uses). Older
+ /*
+ * This is a vmcall instruction (same thing that KVM uses). Older
* assembler versions might not know the "vmcall" instruction, so we
- * create one manually here. */
+ * create one manually here.
+ */
.byte 0x0f,0x01,0xc1 /* KVM_HYPERCALL */
popl %eax
ret
-/* Finally, the "popf" or "restore flags" routine. The %eax register holds the
+/*
+ * Finally, the "popf" or "restore flags" routine. The %eax register holds the
* flags (in practice, either X86_EFLAGS_IF or 0): if it's X86_EFLAGS_IF we're
- * enabling interrupts again, if it's 0 we're leaving them off. */
+ * enabling interrupts again, if it's 0 we're leaving them off.
+ */
ENTRY(lg_restore_fl)
/* This is just "lguest_data.irq_enabled = flags;" */
movl %eax, lguest_data+LGUEST_DATA_irq_enabled
- /* Now, if the %eax value has enabled interrupts and
+ /*
+ * Now, if the %eax value has enabled interrupts and
* lguest_data.irq_pending is set, we want to tell the Host so it can
* deliver any outstanding interrupts. Fortunately, both values will
* be X86_EFLAGS_IF (ie. 512) in that case, and the "testl"
* instruction will AND them together for us. If both are set, we
- * jump to send_interrupts. */
+ * jump to send_interrupts.
+ */
testl lguest_data+LGUEST_DATA_irq_pending, %eax
jnz send_interrupts
/* Again, the normal path has used no extra registers. Clever, huh? */
.global lguest_noirq_start
.global lguest_noirq_end
-/*M:004 When the Host reflects a trap or injects an interrupt into the Guest,
- * it sets the eflags interrupt bit on the stack based on
- * lguest_data.irq_enabled, so the Guest iret logic does the right thing when
- * restoring it. However, when the Host sets the Guest up for direct traps,
- * such as system calls, the processor is the one to push eflags onto the
- * stack, and the interrupt bit will be 1 (in reality, interrupts are always
- * enabled in the Guest).
+/*M:004
+ * When the Host reflects a trap or injects an interrupt into the Guest, it
+ * sets the eflags interrupt bit on the stack based on lguest_data.irq_enabled,
+ * so the Guest iret logic does the right thing when restoring it. However,
+ * when the Host sets the Guest up for direct traps, such as system calls, the
+ * processor is the one to push eflags onto the stack, and the interrupt bit
+ * will be 1 (in reality, interrupts are always enabled in the Guest).
*
* This turns out to be harmless: the only trap which should happen under Linux
* with interrupts disabled is Page Fault (due to our lazy mapping of vmalloc
* regions), which has to be reflected through the Host anyway. If another
* trap *does* go off when interrupts are disabled, the Guest will panic, and
- * we'll never get to this iret! :*/
+ * we'll never get to this iret!
+:*/
-/*G:045 There is one final paravirt_op that the Guest implements, and glancing
- * at it you can see why I left it to last. It's *cool*! It's in *assembler*!
+/*G:045
+ * There is one final paravirt_op that the Guest implements, and glancing at it
+ * you can see why I left it to last. It's *cool*! It's in *assembler*!
*
* The "iret" instruction is used to return from an interrupt or trap. The
* stack looks like this:
* return to userspace or wherever. Our solution to this is to surround the
* code with lguest_noirq_start: and lguest_noirq_end: labels. We tell the
* Host that it is *never* to interrupt us there, even if interrupts seem to be
- * enabled. */
+ * enabled.
+ */
ENTRY(lguest_iret)
pushl %eax
movl 12(%esp), %eax
lguest_noirq_start:
- /* Note the %ss: segment prefix here. Normal data accesses use the
+ /*
+ * Note the %ss: segment prefix here. Normal data accesses use the
* "ds" segment, but that will have already been restored for whatever
* we're returning to (such as userspace): we can't trust it. The %ss:
- * prefix makes sure we use the stack segment, which is still valid. */
+ * prefix makes sure we use the stack segment, which is still valid.
+ */
movl %eax,%ss:lguest_data+LGUEST_DATA_irq_enabled
popl %eax
iret
-/*P:400 This contains run_guest() which actually calls into the Host<->Guest
+/*P:400
+ * This contains run_guest() which actually calls into the Host<->Guest
* Switcher and analyzes the return, such as determining if the Guest wants the
- * Host to do something. This file also contains useful helper routines. :*/
+ * Host to do something. This file also contains useful helper routines.
+:*/
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/stddef.h>
/* This One Big lock protects all inter-guest data structures. */
DEFINE_MUTEX(lguest_lock);
-/*H:010 We need to set up the Switcher at a high virtual address. Remember the
+/*H:010
+ * We need to set up the Switcher at a high virtual address. Remember the
* Switcher is a few hundred bytes of assembler code which actually changes the
* CPU to run the Guest, and then changes back to the Host when a trap or
* interrupt happens.
* Host since it will be running as the switchover occurs.
*
* Trying to map memory at a particular address is an unusual thing to do, so
- * it's not a simple one-liner. */
+ * it's not a simple one-liner.
+ */
static __init int map_switcher(void)
{
int i, err;
* easy.
*/
- /* We allocate an array of struct page pointers. map_vm_area() wants
- * this, rather than just an array of pages. */
+ /*
+ * We allocate an array of struct page pointers. map_vm_area() wants
+ * this, rather than just an array of pages.
+ */
switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
GFP_KERNEL);
if (!switcher_page) {
goto out;
}
- /* Now we actually allocate the pages. The Guest will see these pages,
- * so we make sure they're zeroed. */
+ /*
+ * Now we actually allocate the pages. The Guest will see these pages,
+ * so we make sure they're zeroed.
+ */
for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
unsigned long addr = get_zeroed_page(GFP_KERNEL);
if (!addr) {
switcher_page[i] = virt_to_page(addr);
}
- /* First we check that the Switcher won't overlap the fixmap area at
+ /*
+ * First we check that the Switcher won't overlap the fixmap area at
* the top of memory. It's currently nowhere near, but it could have
- * very strange effects if it ever happened. */
+ * very strange effects if it ever happened.
+ */
if (SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){
err = -ENOMEM;
printk("lguest: mapping switcher would thwack fixmap\n");
goto free_pages;
}
- /* Now we reserve the "virtual memory area" we want: 0xFFC00000
+ /*
+ * Now we reserve the "virtual memory area" we want: 0xFFC00000
* (SWITCHER_ADDR). We might not get it in theory, but in practice
* it's worked so far. The end address needs +1 because __get_vm_area
- * allocates an extra guard page, so we need space for that. */
+ * allocates an extra guard page, so we need space for that.
+ */
switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
VM_ALLOC, SWITCHER_ADDR, SWITCHER_ADDR
+ (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE);
goto free_pages;
}
- /* This code actually sets up the pages we've allocated to appear at
+ /*
+ * This code actually sets up the pages we've allocated to appear at
* SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the
* kind of pages we're mapping (kernel pages), and a pointer to our
* array of struct pages. It increments that pointer, but we don't
- * care. */
+ * care.
+ */
pagep = switcher_page;
err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep);
if (err) {
goto free_vma;
}
- /* Now the Switcher is mapped at the right address, we can't fail!
- * Copy in the compiled-in Switcher code (from <arch>_switcher.S). */
+ /*
+ * Now the Switcher is mapped at the right address, we can't fail!
+ * Copy in the compiled-in Switcher code (from <arch>_switcher.S).
+ */
memcpy(switcher_vma->addr, start_switcher_text,
end_switcher_text - start_switcher_text);
}
/*:*/
-/* Cleaning up the mapping when the module is unloaded is almost...
- * too easy. */
+/* Cleaning up the mapping when the module is unloaded is almost... too easy. */
static void unmap_switcher(void)
{
unsigned int i;
* But we can't trust the Guest: it might be trying to access the Launcher
* code. We have to check that the range is below the pfn_limit the Launcher
* gave us. We have to make sure that addr + len doesn't give us a false
- * positive by overflowing, too. */
+ * positive by overflowing, too.
+ */
bool lguest_address_ok(const struct lguest *lg,
unsigned long addr, unsigned long len)
{
return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
}
-/* This routine copies memory from the Guest. Here we can see how useful the
+/*
+ * This routine copies memory from the Guest. Here we can see how useful the
* kill_lguest() routine we met in the Launcher can be: we return a random
- * value (all zeroes) instead of needing to return an error. */
+ * value (all zeroes) instead of needing to return an error.
+ */
void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes)
{
if (!lguest_address_ok(cpu->lg, addr, bytes)
}
/*:*/
-/*H:030 Let's jump straight to the the main loop which runs the Guest.
+/*H:030
+ * Let's jump straight to the the main loop which runs the Guest.
* Remember, this is called by the Launcher reading /dev/lguest, and we keep
- * going around and around until something interesting happens. */
+ * going around and around until something interesting happens.
+ */
int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
{
/* We stop running once the Guest is dead. */
if (cpu->hcall)
do_hypercalls(cpu);
- /* It's possible the Guest did a NOTIFY hypercall to the
- * Launcher, in which case we return from the read() now. */
+ /*
+ * It's possible the Guest did a NOTIFY hypercall to the
+ * Launcher, in which case we return from the read() now.
+ */
if (cpu->pending_notify) {
if (!send_notify_to_eventfd(cpu)) {
if (put_user(cpu->pending_notify, user))
if (signal_pending(current))
return -ERESTARTSYS;
- /* Check if there are any interrupts which can be delivered now:
+ /*
+ * Check if there are any interrupts which can be delivered now:
* if so, this sets up the hander to be executed when we next
- * run the Guest. */
+ * run the Guest.
+ */
irq = interrupt_pending(cpu, &more);
if (irq < LGUEST_IRQS)
try_deliver_interrupt(cpu, irq, more);
- /* All long-lived kernel loops need to check with this horrible
+ /*
+ * All long-lived kernel loops need to check with this horrible
* thing called the freezer. If the Host is trying to suspend,
- * it stops us. */
+ * it stops us.
+ */
try_to_freeze();
- /* Just make absolutely sure the Guest is still alive. One of
- * those hypercalls could have been fatal, for example. */
+ /*
+ * Just make absolutely sure the Guest is still alive. One of
+ * those hypercalls could have been fatal, for example.
+ */
if (cpu->lg->dead)
break;
- /* If the Guest asked to be stopped, we sleep. The Guest's
- * clock timer will wake us. */
+ /*
+ * If the Guest asked to be stopped, we sleep. The Guest's
+ * clock timer will wake us.
+ */
if (cpu->halted) {
set_current_state(TASK_INTERRUPTIBLE);
- /* Just before we sleep, make sure no interrupt snuck in
- * which we should be doing. */
+ /*
+ * Just before we sleep, make sure no interrupt snuck in
+ * which we should be doing.
+ */
if (interrupt_pending(cpu, &more) < LGUEST_IRQS)
set_current_state(TASK_RUNNING);
else
continue;
}
- /* OK, now we're ready to jump into the Guest. First we put up
- * the "Do Not Disturb" sign: */
+ /*
+ * OK, now we're ready to jump into the Guest. First we put up
+ * the "Do Not Disturb" sign:
+ */
local_irq_disable();
/* Actually run the Guest until something happens. */
}
/*:*/
-/* The Host side of lguest can be a module. This is a nice way for people to
- * play with it. */
+/*
+ * The Host side of lguest can be a module. This is a nice way for people to
+ * play with it.
+ */
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
-/*P:500 Just as userspace programs request kernel operations through a system
+/*P:500
+ * Just as userspace programs request kernel operations through a system
* call, the Guest requests Host operations through a "hypercall". You might
* notice this nomenclature doesn't really follow any logic, but the name has
* been around for long enough that we're stuck with it. As you'd expect, this
- * code is basically a one big switch statement. :*/
+ * code is basically a one big switch statement.
+:*/
/* Copyright (C) 2006 Rusty Russell IBM Corporation
#include <asm/pgtable.h>
#include "lg.h"
-/*H:120 This is the core hypercall routine: where the Guest gets what it wants.
- * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. */
+/*H:120
+ * This is the core hypercall routine: where the Guest gets what it wants.
+ * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both.
+ */
static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
{
switch (args->arg0) {
case LHCALL_FLUSH_ASYNC:
- /* This call does nothing, except by breaking out of the Guest
- * it makes us process all the asynchronous hypercalls. */
+ /*
+ * This call does nothing, except by breaking out of the Guest
+ * it makes us process all the asynchronous hypercalls.
+ */
break;
case LHCALL_SEND_INTERRUPTS:
- /* This call does nothing too, but by breaking out of the Guest
- * it makes us process any pending interrupts. */
+ /*
+ * This call does nothing too, but by breaking out of the Guest
+ * it makes us process any pending interrupts.
+ */
break;
case LHCALL_LGUEST_INIT:
- /* You can't get here unless you're already initialized. Don't
- * do that. */
+ /*
+ * You can't get here unless you're already initialized. Don't
+ * do that.
+ */
kill_guest(cpu, "already have lguest_data");
break;
case LHCALL_SHUTDOWN: {
- /* Shutdown is such a trivial hypercall that we do it in four
- * lines right here. */
char msg[128];
- /* If the lgread fails, it will call kill_guest() itself; the
- * kill_guest() with the message will be ignored. */
+ /*
+ * Shutdown is such a trivial hypercall that we do it in four
+ * lines right here.
+ *
+ * If the lgread fails, it will call kill_guest() itself; the
+ * kill_guest() with the message will be ignored.
+ */
__lgread(cpu, msg, args->arg1, sizeof(msg));
msg[sizeof(msg)-1] = '\0';
kill_guest(cpu, "CRASH: %s", msg);
break;
}
case LHCALL_FLUSH_TLB:
- /* FLUSH_TLB comes in two flavors, depending on the
- * argument: */
+ /* FLUSH_TLB comes in two flavors, depending on the argument: */
if (args->arg1)
guest_pagetable_clear_all(cpu);
else
guest_pagetable_flush_user(cpu);
break;
- /* All these calls simply pass the arguments through to the right
- * routines. */
+ /*
+ * All these calls simply pass the arguments through to the right
+ * routines.
+ */
case LHCALL_NEW_PGTABLE:
guest_new_pagetable(cpu, args->arg1);
break;
kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
}
}
-/*:*/
-/*H:124 Asynchronous hypercalls are easy: we just look in the array in the
+/*H:124
+ * Asynchronous hypercalls are easy: we just look in the array in the
* Guest's "struct lguest_data" to see if any new ones are marked "ready".
*
* We are careful to do these in order: obviously we respect the order the
* Guest put them in the ring, but we also promise the Guest that they will
* happen before any normal hypercall (which is why we check this before
- * checking for a normal hcall). */
+ * checking for a normal hcall).
+ */
static void do_async_hcalls(struct lg_cpu *cpu)
{
unsigned int i;
/* We process "struct lguest_data"s hcalls[] ring once. */
for (i = 0; i < ARRAY_SIZE(st); i++) {
struct hcall_args args;
- /* We remember where we were up to from last time. This makes
+ /*
+ * We remember where we were up to from last time. This makes
* sure that the hypercalls are done in the order the Guest
- * places them in the ring. */
+ * places them in the ring.
+ */
unsigned int n = cpu->next_hcall;
/* 0xFF means there's no call here (yet). */
if (st[n] == 0xFF)
break;
- /* OK, we have hypercall. Increment the "next_hcall" cursor,
- * and wrap back to 0 if we reach the end. */
+ /*
+ * OK, we have hypercall. Increment the "next_hcall" cursor,
+ * and wrap back to 0 if we reach the end.
+ */
if (++cpu->next_hcall == LHCALL_RING_SIZE)
cpu->next_hcall = 0;
- /* Copy the hypercall arguments into a local copy of
- * the hcall_args struct. */
+ /*
+ * Copy the hypercall arguments into a local copy of the
+ * hcall_args struct.
+ */
if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
sizeof(struct hcall_args))) {
kill_guest(cpu, "Fetching async hypercalls");
break;
}
- /* Stop doing hypercalls if they want to notify the Launcher:
- * it needs to service this first. */
+ /*
+ * Stop doing hypercalls if they want to notify the Launcher:
+ * it needs to service this first.
+ */
if (cpu->pending_notify)
break;
}
}
-/* Last of all, we look at what happens first of all. The very first time the
- * Guest makes a hypercall, we end up here to set things up: */
+/*
+ * Last of all, we look at what happens first of all. The very first time the
+ * Guest makes a hypercall, we end up here to set things up:
+ */
static void initialize(struct lg_cpu *cpu)
{
- /* You can't do anything until you're initialized. The Guest knows the
- * rules, so we're unforgiving here. */
+ /*
+ * You can't do anything until you're initialized. The Guest knows the
+ * rules, so we're unforgiving here.
+ */
if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
return;
if (lguest_arch_init_hypercalls(cpu))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
- /* The Guest tells us where we're not to deliver interrupts by putting
- * the range of addresses into "struct lguest_data". */
+ /*
+ * The Guest tells us where we're not to deliver interrupts by putting
+ * the range of addresses into "struct lguest_data".
+ */
if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
|| get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
- /* We write the current time into the Guest's data page once so it can
- * set its clock. */
+ /*
+ * We write the current time into the Guest's data page once so it can
+ * set its clock.
+ */
write_timestamp(cpu);
/* page_tables.c will also do some setup. */
page_table_guest_data_init(cpu);
- /* This is the one case where the above accesses might have been the
+ /*
+ * This is the one case where the above accesses might have been the
* first write to a Guest page. This may have caused a copy-on-write
* fault, but the old page might be (read-only) in the Guest
- * pagetable. */
+ * pagetable.
+ */
guest_pagetable_clear_all(cpu);
}
/*:*/
-/*M:013 If a Guest reads from a page (so creates a mapping) that it has never
+/*M:013
+ * If a Guest reads from a page (so creates a mapping) that it has never
* written to, and then the Launcher writes to it (ie. the output of a virtual
* device), the Guest will still see the old page. In practice, this never
* happens: why would the Guest read a page which it has never written to? But
- * a similar scenario might one day bite us, so it's worth mentioning. :*/
+ * a similar scenario might one day bite us, so it's worth mentioning.
+:*/
/*H:100
* Hypercalls
return;
}
- /* The Guest has initialized.
+ /*
+ * The Guest has initialized.
*
- * Look in the hypercall ring for the async hypercalls: */
+ * Look in the hypercall ring for the async hypercalls:
+ */
do_async_hcalls(cpu);
- /* If we stopped reading the hypercall ring because the Guest did a
+ /*
+ * If we stopped reading the hypercall ring because the Guest did a
* NOTIFY to the Launcher, we want to return now. Otherwise we do
- * the hypercall. */
+ * the hypercall.
+ */
if (!cpu->pending_notify) {
do_hcall(cpu, cpu->hcall);
- /* Tricky point: we reset the hcall pointer to mark the
+ /*
+ * Tricky point: we reset the hcall pointer to mark the
* hypercall as "done". We use the hcall pointer rather than
* the trap number to indicate a hypercall is pending.
* Normally it doesn't matter: the Guest will run again and
* However, if we are signalled or the Guest sends I/O to the
* Launcher, the run_guest() loop will exit without running the
* Guest. When it comes back it would try to re-run the
- * hypercall. Finding that bug sucked. */
+ * hypercall. Finding that bug sucked.
+ */
cpu->hcall = NULL;
}
}
-/* This routine supplies the Guest with time: it's used for wallclock time at
- * initial boot and as a rough time source if the TSC isn't available. */
+/*
+ * This routine supplies the Guest with time: it's used for wallclock time at
+ * initial boot and as a rough time source if the TSC isn't available.
+ */
void write_timestamp(struct lg_cpu *cpu)
{
struct timespec now;
-/*P:800 Interrupts (traps) are complicated enough to earn their own file.
+/*P:800
+ * Interrupts (traps) are complicated enough to earn their own file.
* There are three classes of interrupts:
*
* 1) Real hardware interrupts which occur while we're running the Guest,
* just like real hardware would deliver them. Traps from the Guest can be set
* up to go directly back into the Guest, but sometimes the Host wants to see
* them first, so we also have a way of "reflecting" them into the Guest as if
- * they had been delivered to it directly. :*/
+ * they had been delivered to it directly.
+:*/
#include <linux/uaccess.h>
#include <linux/interrupt.h>
#include <linux/module.h>
return (lo & 0x0000FFFF) | (hi & 0xFFFF0000);
}
-/* The "type" of the interrupt handler is a 4 bit field: we only support a
- * couple of types. */
+/*
+ * The "type" of the interrupt handler is a 4 bit field: we only support a
+ * couple of types.
+ */
static int idt_type(u32 lo, u32 hi)
{
return (hi >> 8) & 0xF;
return (hi & 0x8000);
}
-/* We need a helper to "push" a value onto the Guest's stack, since that's a
- * big part of what delivering an interrupt does. */
+/*
+ * We need a helper to "push" a value onto the Guest's stack, since that's a
+ * big part of what delivering an interrupt does.
+ */
static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val)
{
/* Stack grows upwards: move stack then write value. */
lgwrite(cpu, *gstack, u32, val);
}
-/*H:210 The set_guest_interrupt() routine actually delivers the interrupt or
+/*H:210
+ * The set_guest_interrupt() routine actually delivers the interrupt or
* trap. The mechanics of delivering traps and interrupts to the Guest are the
* same, except some traps have an "error code" which gets pushed onto the
* stack as well: the caller tells us if this is one.
*
* We set up the stack just like the CPU does for a real interrupt, so it's
* identical for the Guest (and the standard "iret" instruction will undo
- * it). */
+ * it).
+ */
static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
bool has_err)
{
u32 eflags, ss, irq_enable;
unsigned long virtstack;
- /* There are two cases for interrupts: one where the Guest is already
+ /*
+ * There are two cases for interrupts: one where the Guest is already
* in the kernel, and a more complex one where the Guest is in
- * userspace. We check the privilege level to find out. */
+ * userspace. We check the privilege level to find out.
+ */
if ((cpu->regs->ss&0x3) != GUEST_PL) {
- /* The Guest told us their kernel stack with the SET_STACK
- * hypercall: both the virtual address and the segment */
+ /*
+ * The Guest told us their kernel stack with the SET_STACK
+ * hypercall: both the virtual address and the segment.
+ */
virtstack = cpu->esp1;
ss = cpu->ss1;
origstack = gstack = guest_pa(cpu, virtstack);
- /* We push the old stack segment and pointer onto the new
+ /*
+ * We push the old stack segment and pointer onto the new
* stack: when the Guest does an "iret" back from the interrupt
* handler the CPU will notice they're dropping privilege
- * levels and expect these here. */
+ * levels and expect these here.
+ */
push_guest_stack(cpu, &gstack, cpu->regs->ss);
push_guest_stack(cpu, &gstack, cpu->regs->esp);
} else {
origstack = gstack = guest_pa(cpu, virtstack);
}
- /* Remember that we never let the Guest actually disable interrupts, so
+ /*
+ * Remember that we never let the Guest actually disable interrupts, so
* the "Interrupt Flag" bit is always set. We copy that bit from the
* Guest's "irq_enabled" field into the eflags word: we saw the Guest
- * copy it back in "lguest_iret". */
+ * copy it back in "lguest_iret".
+ */
eflags = cpu->regs->eflags;
if (get_user(irq_enable, &cpu->lg->lguest_data->irq_enabled) == 0
&& !(irq_enable & X86_EFLAGS_IF))
eflags &= ~X86_EFLAGS_IF;
- /* An interrupt is expected to push three things on the stack: the old
+ /*
+ * An interrupt is expected to push three things on the stack: the old
* "eflags" word, the old code segment, and the old instruction
- * pointer. */
+ * pointer.
+ */
push_guest_stack(cpu, &gstack, eflags);
push_guest_stack(cpu, &gstack, cpu->regs->cs);
push_guest_stack(cpu, &gstack, cpu->regs->eip);
if (has_err)
push_guest_stack(cpu, &gstack, cpu->regs->errcode);
- /* Now we've pushed all the old state, we change the stack, the code
- * segment and the address to execute. */
+ /*
+ * Now we've pushed all the old state, we change the stack, the code
+ * segment and the address to execute.
+ */
cpu->regs->ss = ss;
cpu->regs->esp = virtstack + (gstack - origstack);
cpu->regs->cs = (__KERNEL_CS|GUEST_PL);
cpu->regs->eip = idt_address(lo, hi);
- /* There are two kinds of interrupt handlers: 0xE is an "interrupt
- * gate" which expects interrupts to be disabled on entry. */
+ /*
+ * There are two kinds of interrupt handlers: 0xE is an "interrupt
+ * gate" which expects interrupts to be disabled on entry.
+ */
if (idt_type(lo, hi) == 0xE)
if (put_user(0, &cpu->lg->lguest_data->irq_enabled))
kill_guest(cpu, "Disabling interrupts");
*
* interrupt_pending() returns the first pending interrupt which isn't blocked
* by the Guest. It is called before every entry to the Guest, and just before
- * we go to sleep when the Guest has halted itself. */
+ * we go to sleep when the Guest has halted itself.
+ */
unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more)
{
unsigned int irq;
if (!cpu->lg->lguest_data)
return LGUEST_IRQS;
- /* Take our "irqs_pending" array and remove any interrupts the Guest
- * wants blocked: the result ends up in "blk". */
+ /*
+ * Take our "irqs_pending" array and remove any interrupts the Guest
+ * wants blocked: the result ends up in "blk".
+ */
if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts,
sizeof(blk)))
return LGUEST_IRQS;
return irq;
}
-/* This actually diverts the Guest to running an interrupt handler, once an
- * interrupt has been identified by interrupt_pending(). */
+/*
+ * This actually diverts the Guest to running an interrupt handler, once an
+ * interrupt has been identified by interrupt_pending().
+ */
void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
{
struct desc_struct *idt;
BUG_ON(irq >= LGUEST_IRQS);
- /* They may be in the middle of an iret, where they asked us never to
- * deliver interrupts. */
+ /*
+ * They may be in the middle of an iret, where they asked us never to
+ * deliver interrupts.
+ */
if (cpu->regs->eip >= cpu->lg->noirq_start &&
(cpu->regs->eip < cpu->lg->noirq_end))
return;
}
}
- /* Look at the IDT entry the Guest gave us for this interrupt. The
+ /*
+ * Look at the IDT entry the Guest gave us for this interrupt. The
* first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip
- * over them. */
+ * over them.
+ */
idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq];
/* If they don't have a handler (yet?), we just ignore it */
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
clear_bit(irq, cpu->irqs_pending);
- /* set_guest_interrupt() takes the interrupt descriptor and a
+ /*
+ * set_guest_interrupt() takes the interrupt descriptor and a
* flag to say whether this interrupt pushes an error code onto
- * the stack as well: virtual interrupts never do. */
+ * the stack as well: virtual interrupts never do.
+ */
set_guest_interrupt(cpu, idt->a, idt->b, false);
}
- /* Every time we deliver an interrupt, we update the timestamp in the
+ /*
+ * Every time we deliver an interrupt, we update the timestamp in the
* Guest's lguest_data struct. It would be better for the Guest if we
* did this more often, but it can actually be quite slow: doing it
* here is a compromise which means at least it gets updated every
- * timer interrupt. */
+ * timer interrupt.
+ */
write_timestamp(cpu);
- /* If there are no other interrupts we want to deliver, clear
- * the pending flag. */
+ /*
+ * If there are no other interrupts we want to deliver, clear
+ * the pending flag.
+ */
if (!more)
put_user(0, &cpu->lg->lguest_data->irq_pending);
}
/* And this is the routine when we want to set an interrupt for the Guest. */
void set_interrupt(struct lg_cpu *cpu, unsigned int irq)
{
- /* Next time the Guest runs, the core code will see if it can deliver
- * this interrupt. */
+ /*
+ * Next time the Guest runs, the core code will see if it can deliver
+ * this interrupt.
+ */
set_bit(irq, cpu->irqs_pending);
- /* Make sure it sees it; it might be asleep (eg. halted), or
- * running the Guest right now, in which case kick_process()
- * will knock it out. */
+ /*
+ * Make sure it sees it; it might be asleep (eg. halted), or running
+ * the Guest right now, in which case kick_process() will knock it out.
+ */
if (!wake_up_process(cpu->tsk))
kick_process(cpu->tsk);
}
/*:*/
-/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent
+/*
+ * Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent
* me a patch, so we support that too. It'd be a big step for lguest if half
* the Plan 9 user base were to start using it.
*
* Actually now I think of it, it's possible that Ron *is* half the Plan 9
- * userbase. Oh well. */
+ * userbase. Oh well.
+ */
static bool could_be_syscall(unsigned int num)
{
/* Normal Linux SYSCALL_VECTOR or reserved vector? */
clear_bit(syscall_vector, used_vectors);
}
-/*H:220 Now we've got the routines to deliver interrupts, delivering traps like
+/*H:220
+ * Now we've got the routines to deliver interrupts, delivering traps like
* page fault is easy. The only trick is that Intel decided that some traps
- * should have error codes: */
+ * should have error codes:
+ */
static bool has_err(unsigned int trap)
{
return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17);
/* deliver_trap() returns true if it could deliver the trap. */
bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
{
- /* Trap numbers are always 8 bit, but we set an impossible trap number
- * for traps inside the Switcher, so check that here. */
+ /*
+ * Trap numbers are always 8 bit, but we set an impossible trap number
+ * for traps inside the Switcher, so check that here.
+ */
if (num >= ARRAY_SIZE(cpu->arch.idt))
return false;
- /* Early on the Guest hasn't set the IDT entries (or maybe it put a
- * bogus one in): if we fail here, the Guest will be killed. */
+ /*
+ * Early on the Guest hasn't set the IDT entries (or maybe it put a
+ * bogus one in): if we fail here, the Guest will be killed.
+ */
if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b))
return false;
set_guest_interrupt(cpu, cpu->arch.idt[num].a,
return true;
}
-/*H:250 Here's the hard part: returning to the Host every time a trap happens
+/*H:250
+ * Here's the hard part: returning to the Host every time a trap happens
* and then calling deliver_trap() and re-entering the Guest is slow.
* Particularly because Guest userspace system calls are traps (usually trap
* 128).
* the other hypervisors would beat it up at lunchtime.
*
* This routine indicates if a particular trap number could be delivered
- * directly. */
+ * directly.
+ */
static bool direct_trap(unsigned int num)
{
- /* Hardware interrupts don't go to the Guest at all (except system
- * call). */
+ /*
+ * Hardware interrupts don't go to the Guest at all (except system
+ * call).
+ */
if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num))
return false;
- /* The Host needs to see page faults (for shadow paging and to save the
+ /*
+ * The Host needs to see page faults (for shadow paging and to save the
* fault address), general protection faults (in/out emulation) and
* device not available (TS handling), invalid opcode fault (kvm hcall),
- * and of course, the hypercall trap. */
+ * and of course, the hypercall trap.
+ */
return num != 14 && num != 13 && num != 7 &&
num != 6 && num != LGUEST_TRAP_ENTRY;
}
/*:*/
-/*M:005 The Guest has the ability to turn its interrupt gates into trap gates,
+/*M:005
+ * The Guest has the ability to turn its interrupt gates into trap gates,
* if it is careful. The Host will let trap gates can go directly to the
* Guest, but the Guest needs the interrupts atomically disabled for an
* interrupt gate. It can do this by pointing the trap gate at instructions
- * within noirq_start and noirq_end, where it can safely disable interrupts. */
+ * within noirq_start and noirq_end, where it can safely disable interrupts.
+ */
-/*M:006 The Guests do not use the sysenter (fast system call) instruction,
+/*M:006
+ * The Guests do not use the sysenter (fast system call) instruction,
* because it's hardcoded to enter privilege level 0 and so can't go direct.
* It's about twice as fast as the older "int 0x80" system call, so it might
* still be worthwhile to handle it in the Switcher and lcall down to the
* Guest. The sysenter semantics are hairy tho: search for that keyword in
- * entry.S :*/
+ * entry.S
+:*/
-/*H:260 When we make traps go directly into the Guest, we need to make sure
+/*H:260
+ * When we make traps go directly into the Guest, we need to make sure
* the kernel stack is valid (ie. mapped in the page tables). Otherwise, the
* CPU trying to deliver the trap will fault while trying to push the interrupt
* words on the stack: this is called a double fault, and it forces us to kill
* the Guest.
*
- * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. */
+ * Which is deeply unfair, because (literally!) it wasn't the Guests' fault.
+ */
void pin_stack_pages(struct lg_cpu *cpu)
{
unsigned int i;
- /* Depending on the CONFIG_4KSTACKS option, the Guest can have one or
- * two pages of stack space. */
+ /*
+ * Depending on the CONFIG_4KSTACKS option, the Guest can have one or
+ * two pages of stack space.
+ */
for (i = 0; i < cpu->lg->stack_pages; i++)
- /* The stack grows *upwards*, so the address we're given is the
+ /*
+ * The stack grows *upwards*, so the address we're given is the
* start of the page after the kernel stack. Subtract one to
* get back onto the first stack page, and keep subtracting to
- * get to the rest of the stack pages. */
+ * get to the rest of the stack pages.
+ */
pin_page(cpu, cpu->esp1 - 1 - i * PAGE_SIZE);
}
-/* Direct traps also mean that we need to know whenever the Guest wants to use
+/*
+ * Direct traps also mean that we need to know whenever the Guest wants to use
* a different kernel stack, so we can change the IDT entries to use that
* stack. The IDT entries expect a virtual address, so unlike most addresses
* the Guest gives us, the "esp" (stack pointer) value here is virtual, not
* physical.
*
* In Linux each process has its own kernel stack, so this happens a lot: we
- * change stacks on each context switch. */
+ * change stacks on each context switch.
+ */
void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages)
{
- /* You are not allowed have a stack segment with privilege level 0: bad
- * Guest! */
+ /*
+ * You're not allowed a stack segment with privilege level 0: bad Guest!
+ */
if ((seg & 0x3) != GUEST_PL)
kill_guest(cpu, "bad stack segment %i", seg);
/* We only expect one or two stack pages. */
pin_stack_pages(cpu);
}
-/* All this reference to mapping stacks leads us neatly into the other complex
- * part of the Host: page table handling. */
+/*
+ * All this reference to mapping stacks leads us neatly into the other complex
+ * part of the Host: page table handling.
+ */
-/*H:235 This is the routine which actually checks the Guest's IDT entry and
- * transfers it into the entry in "struct lguest": */
+/*H:235
+ * This is the routine which actually checks the Guest's IDT entry and
+ * transfers it into the entry in "struct lguest":
+ */
static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap,
unsigned int num, u32 lo, u32 hi)
{
if (type != 0xE && type != 0xF)
kill_guest(cpu, "bad IDT type %i", type);
- /* We only copy the handler address, present bit, privilege level and
+ /*
+ * We only copy the handler address, present bit, privilege level and
* type. The privilege level controls where the trap can be triggered
* manually with an "int" instruction. This is usually GUEST_PL,
- * except for system calls which userspace can use. */
+ * except for system calls which userspace can use.
+ */
trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF);
trap->b = (hi&0xFFFFEF00);
}
-/*H:230 While we're here, dealing with delivering traps and interrupts to the
+/*H:230
+ * While we're here, dealing with delivering traps and interrupts to the
* Guest, we might as well complete the picture: how the Guest tells us where
* it wants them to go. This would be simple, except making traps fast
* requires some tricks.
*
* We saw the Guest setting Interrupt Descriptor Table (IDT) entries with the
- * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. */
+ * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here.
+ */
void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi)
{
- /* Guest never handles: NMI, doublefault, spurious interrupt or
- * hypercall. We ignore when it tries to set them. */
+ /*
+ * Guest never handles: NMI, doublefault, spurious interrupt or
+ * hypercall. We ignore when it tries to set them.
+ */
if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY)
return;
- /* Mark the IDT as changed: next time the Guest runs we'll know we have
- * to copy this again. */
+ /*
+ * Mark the IDT as changed: next time the Guest runs we'll know we have
+ * to copy this again.
+ */
cpu->changed |= CHANGED_IDT;
/* Check that the Guest doesn't try to step outside the bounds. */
set_trap(cpu, &cpu->arch.idt[num], num, lo, hi);
}
-/* The default entry for each interrupt points into the Switcher routines which
+/*
+ * The default entry for each interrupt points into the Switcher routines which
* simply return to the Host. The run_guest() loop will then call
- * deliver_trap() to bounce it back into the Guest. */
+ * deliver_trap() to bounce it back into the Guest.
+ */
static void default_idt_entry(struct desc_struct *idt,
int trap,
const unsigned long handler,
/* A present interrupt gate. */
u32 flags = 0x8e00;
- /* Set the privilege level on the entry for the hypercall: this allows
- * the Guest to use the "int" instruction to trigger it. */
+ /*
+ * Set the privilege level on the entry for the hypercall: this allows
+ * the Guest to use the "int" instruction to trigger it.
+ */
if (trap == LGUEST_TRAP_ENTRY)
flags |= (GUEST_PL << 13);
else if (base)
- /* Copy priv. level from what Guest asked for. This allows
- * debug (int 3) traps from Guest userspace, for example. */
+ /*
+ * Copy privilege level from what Guest asked for. This allows
+ * debug (int 3) traps from Guest userspace, for example.
+ */
flags |= (base->b & 0x6000);
/* Now pack it into the IDT entry in its weird format. */
default_idt_entry(&state->guest_idt[i], i, def[i], NULL);
}
-/*H:240 We don't use the IDT entries in the "struct lguest" directly, instead
+/*H:240
+ * We don't use the IDT entries in the "struct lguest" directly, instead
* we copy them into the IDT which we've set up for Guests on this CPU, just
- * before we run the Guest. This routine does that copy. */
+ * before we run the Guest. This routine does that copy.
+ */
void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt,
const unsigned long *def)
{
unsigned int i;
- /* We can simply copy the direct traps, otherwise we use the default
- * ones in the Switcher: they will return to the Host. */
+ /*
+ * We can simply copy the direct traps, otherwise we use the default
+ * ones in the Switcher: they will return to the Host.
+ */
for (i = 0; i < ARRAY_SIZE(cpu->arch.idt); i++) {
const struct desc_struct *gidt = &cpu->arch.idt[i];
if (!direct_trap(i))
continue;
- /* Only trap gates (type 15) can go direct to the Guest.
+ /*
+ * Only trap gates (type 15) can go direct to the Guest.
* Interrupt gates (type 14) disable interrupts as they are
* entered, which we never let the Guest do. Not present
* entries (type 0x0) also can't go direct, of course.
*
* If it can't go direct, we still need to copy the priv. level:
* they might want to give userspace access to a software
- * interrupt. */
+ * interrupt.
+ */
if (idt_type(gidt->a, gidt->b) == 0xF)
idt[i] = *gidt;
else
* the next timer interrupt (in nanoseconds). We use the high-resolution timer
* infrastructure to set a callback at that time.
*
- * 0 means "turn off the clock". */
+ * 0 means "turn off the clock".
+ */
void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta)
{
ktime_t expires;
return;
}
- /* We use wallclock time here, so the Guest might not be running for
+ /*
+ * We use wallclock time here, so the Guest might not be running for
* all the time between now and the timer interrupt it asked for. This
- * is almost always the right thing to do. */
+ * is almost always the right thing to do.
+ */
expires = ktime_add_ns(ktime_get_real(), delta);
hrtimer_start(&cpu->hrt, expires, HRTIMER_MODE_ABS);
}
unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
- /* At end of a page shared mapped over lguest_pages in guest. */
+ /* At end of a page shared mapped over lguest_pages in guest. */
unsigned long regs_page;
struct lguest_regs *regs;
struct lguest_pages *last_pages;
- int cpu_pgd; /* which pgd this cpu is currently using */
+ int cpu_pgd; /* Which pgd this cpu is currently using */
/* If a hypercall was asked for, this points to the arguments. */
struct hcall_args *hcall;
unsigned int nr_cpus;
u32 pfn_limit;
- /* This provides the offset to the base of guest-physical
- * memory in the Launcher. */
+
+ /*
+ * This provides the offset to the base of guest-physical memory in the
+ * Launcher.
+ */
void __user *mem_base;
unsigned long kernel_address;
void __lgread(struct lg_cpu *, void *, unsigned long, unsigned);
void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned);
-/*H:035 Using memory-copy operations like that is usually inconvient, so we
+/*H:035
+ * Using memory-copy operations like that is usually inconvient, so we
* have the following helper macros which read and write a specific type (often
* an unsigned long).
*
- * This reads into a variable of the given type then returns that. */
+ * This reads into a variable of the given type then returns that.
+ */
#define lgread(cpu, addr, type) \
({ type _v; __lgread((cpu), &_v, (addr), sizeof(_v)); _v; })
int run_guest(struct lg_cpu *cpu, unsigned long __user *user);
-/* Helper macros to obtain the first 12 or the last 20 bits, this is only the
+/*
+ * Helper macros to obtain the first 12 or the last 20 bits, this is only the
* first step in the migration to the kernel types. pte_pfn is already defined
- * in the kernel. */
+ * in the kernel.
+ */
#define pgd_flags(x) (pgd_val(x) & ~PAGE_MASK)
#define pgd_pfn(x) (pgd_val(x) >> PAGE_SHIFT)
#define pmd_flags(x) (pmd_val(x) & ~PAGE_MASK)
-/*P:050 Lguest guests use a very simple method to describe devices. It's a
+/*P:050
+ * Lguest guests use a very simple method to describe devices. It's a
* series of device descriptors contained just above the top of normal Guest
* memory.
*
* We use the standard "virtio" device infrastructure, which provides us with a
* console, a network and a block driver. Each one expects some configuration
- * information and a "virtqueue" or two to send and receive data. :*/
+ * information and a "virtqueue" or two to send and receive data.
+:*/
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/lguest_launcher.h>
/* The pointer to our (page) of device descriptions. */
static void *lguest_devices;
-/* For Guests, device memory can be used as normal memory, so we cast away the
- * __iomem to quieten sparse. */
+/*
+ * For Guests, device memory can be used as normal memory, so we cast away the
+ * __iomem to quieten sparse.
+ */
static inline void *lguest_map(unsigned long phys_addr, unsigned long pages)
{
return (__force void *)ioremap_cache(phys_addr, PAGE_SIZE*pages);
iounmap((__force void __iomem *)addr);
}
-/*D:100 Each lguest device is just a virtio device plus a pointer to its entry
- * in the lguest_devices page. */
+/*D:100
+ * Each lguest device is just a virtio device plus a pointer to its entry
+ * in the lguest_devices page.
+ */
struct lguest_device {
struct virtio_device vdev;
struct lguest_device_desc *desc;
};
-/* Since the virtio infrastructure hands us a pointer to the virtio_device all
+/*
+ * Since the virtio infrastructure hands us a pointer to the virtio_device all
* the time, it helps to have a curt macro to get a pointer to the struct
- * lguest_device it's enclosed in. */
+ * lguest_device it's enclosed in.
+ */
#define to_lgdev(vd) container_of(vd, struct lguest_device, vdev)
/*D:130
* the driver will look at them during setup.
*
* A convenient routine to return the device's virtqueue config array:
- * immediately after the descriptor. */
+ * immediately after the descriptor.
+ */
static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc)
{
return (void *)(desc + 1);
return features;
}
-/* The virtio core takes the features the Host offers, and copies the
- * ones supported by the driver into the vdev->features array. Once
- * that's all sorted out, this routine is called so we can tell the
- * Host which features we understand and accept. */
+/*
+ * The virtio core takes the features the Host offers, and copies the ones
+ * supported by the driver into the vdev->features array. Once that's all
+ * sorted out, this routine is called so we can tell the Host which features we
+ * understand and accept.
+ */
static void lg_finalize_features(struct virtio_device *vdev)
{
unsigned int i, bits;
/* Give virtio_ring a chance to accept features. */
vring_transport_features(vdev);
- /* The vdev->feature array is a Linux bitmask: this isn't the
- * same as a the simple array of bits used by lguest devices
- * for features. So we do this slow, manual conversion which is
- * completely general. */
+ /*
+ * The vdev->feature array is a Linux bitmask: this isn't the same as a
+ * the simple array of bits used by lguest devices for features. So we
+ * do this slow, manual conversion which is completely general.
+ */
memset(out_features, 0, desc->feature_len);
bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
for (i = 0; i < bits; i++) {
memcpy(lg_config(desc) + offset, buf, len);
}
-/* The operations to get and set the status word just access the status field
- * of the device descriptor. */
+/*
+ * The operations to get and set the status word just access the status field
+ * of the device descriptor.
+ */
static u8 lg_get_status(struct virtio_device *vdev)
{
return to_lgdev(vdev)->desc->status;
}
-/* To notify on status updates, we (ab)use the NOTIFY hypercall, with the
- * descriptor address of the device. A zero status means "reset". */
+/*
+ * To notify on status updates, we (ab)use the NOTIFY hypercall, with the
+ * descriptor address of the device. A zero status means "reset".
+ */
static void set_status(struct virtio_device *vdev, u8 status)
{
unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
void *pages;
};
-/* When the virtio_ring code wants to prod the Host, it calls us here and we
+/*
+ * When the virtio_ring code wants to prod the Host, it calls us here and we
* make a hypercall. We hand the physical address of the virtqueue so the Host
- * knows which virtqueue we're talking about. */
+ * knows which virtqueue we're talking about.
+ */
static void lg_notify(struct virtqueue *vq)
{
- /* We store our virtqueue information in the "priv" pointer of the
- * virtqueue structure. */
+ /*
+ * We store our virtqueue information in the "priv" pointer of the
+ * virtqueue structure.
+ */
struct lguest_vq_info *lvq = vq->priv;
kvm_hypercall1(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT);
/* An extern declaration inside a C file is bad form. Don't do it. */
extern void lguest_setup_irq(unsigned int irq);
-/* This routine finds the first virtqueue described in the configuration of
+/*
+ * This routine finds the first virtqueue described in the configuration of
* this device and sets it up.
*
* This is kind of an ugly duckling. It'd be nicer to have a standard
* simpler for the Host to simply tell us where the pages are.
*
* So we provide drivers with a "find the Nth virtqueue and set it up"
- * function. */
+ * function.
+ */
static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
unsigned index,
void (*callback)(struct virtqueue *vq),
if (!lvq)
return ERR_PTR(-ENOMEM);
- /* Make a copy of the "struct lguest_vqconfig" entry, which sits after
+ /*
+ * Make a copy of the "struct lguest_vqconfig" entry, which sits after
* the descriptor. We need a copy because the config space might not
- * be aligned correctly. */
+ * be aligned correctly.
+ */
memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config));
printk("Mapping virtqueue %i addr %lx\n", index,
goto free_lvq;
}
- /* OK, tell virtio_ring.c to set up a virtqueue now we know its size
- * and we've got a pointer to its pages. */
+ /*
+ * OK, tell virtio_ring.c to set up a virtqueue now we know its size
+ * and we've got a pointer to its pages.
+ */
vq = vring_new_virtqueue(lvq->config.num, LGUEST_VRING_ALIGN,
vdev, lvq->pages, lg_notify, callback, name);
if (!vq) {
/* Make sure the interrupt is allocated. */
lguest_setup_irq(lvq->config.irq);
- /* Tell the interrupt for this virtqueue to go to the virtio_ring
- * interrupt handler. */
- /* FIXME: We used to have a flag for the Host to tell us we could use
+ /*
+ * Tell the interrupt for this virtqueue to go to the virtio_ring
+ * interrupt handler.
+ *
+ * FIXME: We used to have a flag for the Host to tell us we could use
* the interrupt as a source of randomness: it'd be nice to have that
- * back.. */
+ * back.
+ */
err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED,
dev_name(&vdev->dev), vq);
if (err)
goto destroy_vring;
- /* Last of all we hook up our 'struct lguest_vq_info" to the
- * virtqueue's priv pointer. */
+ /*
+ * Last of all we hook up our 'struct lguest_vq_info" to the
+ * virtqueue's priv pointer.
+ */
vq->priv = lvq;
return vq;
.del_vqs = lg_del_vqs,
};
-/* The root device for the lguest virtio devices. This makes them appear as
- * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. */
+/*
+ * The root device for the lguest virtio devices. This makes them appear as
+ * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2.
+ */
static struct device *lguest_root;
-/*D:120 This is the core of the lguest bus: actually adding a new device.
+/*D:120
+ * This is the core of the lguest bus: actually adding a new device.
* It's a separate function because it's neater that way, and because an
* earlier version of the code supported hotplug and unplug. They were removed
* early on because they were never used.
*
* It's worth reading this carefully: we start with a pointer to the new device
* descriptor in the "lguest_devices" page, and the offset into the device
- * descriptor page so we can uniquely identify it if things go badly wrong. */
+ * descriptor page so we can uniquely identify it if things go badly wrong.
+ */
static void add_lguest_device(struct lguest_device_desc *d,
unsigned int offset)
{
struct lguest_device *ldev;
- /* Start with zeroed memory; Linux's device layer seems to count on
- * it. */
+ /* Start with zeroed memory; Linux's device layer counts on it. */
ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
if (!ldev) {
printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n",
ldev->vdev.dev.parent = lguest_root;
/* We have a unique device index thanks to the dev_index counter. */
ldev->vdev.id.device = d->type;
- /* We have a simple set of routines for querying the device's
- * configuration information and setting its status. */
+ /*
+ * We have a simple set of routines for querying the device's
+ * configuration information and setting its status.
+ */
ldev->vdev.config = &lguest_config_ops;
/* And we remember the device's descriptor for lguest_config_ops. */
ldev->desc = d;
- /* register_virtio_device() sets up the generic fields for the struct
+ /*
+ * register_virtio_device() sets up the generic fields for the struct
* virtio_device and calls device_register(). This makes the bus
- * infrastructure look for a matching driver. */
+ * infrastructure look for a matching driver.
+ */
if (register_virtio_device(&ldev->vdev) != 0) {
printk(KERN_ERR "Failed to register lguest dev %u type %u\n",
offset, d->type);
}
}
-/*D:110 scan_devices() simply iterates through the device page. The type 0 is
- * reserved to mean "end of devices". */
+/*D:110
+ * scan_devices() simply iterates through the device page. The type 0 is
+ * reserved to mean "end of devices".
+ */
static void scan_devices(void)
{
unsigned int i;
}
}
-/*D:105 Fairly early in boot, lguest_devices_init() is called to set up the
+/*D:105
+ * Fairly early in boot, lguest_devices_init() is called to set up the
* lguest device infrastructure. We check that we are a Guest by checking
* pv_info.name: there are other ways of checking, but this seems most
* obvious to me.
* correct sysfs incantation).
*
* Finally we call scan_devices() which adds all the devices found in the
- * lguest_devices page. */
+ * lguest_devices page.
+ */
static int __init lguest_devices_init(void)
{
if (strcmp(pv_info.name, "lguest") != 0)
/* We do this after core stuff, but before the drivers. */
postcore_initcall(lguest_devices_init);
-/*D:150 At this point in the journey we used to now wade through the lguest
+/*D:150
+ * At this point in the journey we used to now wade through the lguest
* devices themselves: net, block and console. Since they're all now virtio
* devices rather than lguest-specific, I've decided to ignore them. Mostly,
* they're kind of boring. But this does mean you'll never experience the
* thrill of reading the forbidden love scene buried deep in the block driver.
*
* "make Launcher" beckons, where we answer questions like "Where do Guests
- * come from?", and "What do you do when someone asks for optimization?". */
+ * come from?", and "What do you do when someone asks for optimization?".
+ */
-/*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
+/*P:200
+ * This contains all the /dev/lguest code, whereby the userspace launcher
* controls and communicates with the Guest. For example, the first write will
* tell us the Guest's memory layout, pagetable, entry point and kernel address
* offset. A read will run the Guest until something happens, such as a signal
- * or the Guest doing a NOTIFY out to the Launcher. :*/
+ * or the Guest doing a NOTIFY out to the Launcher.
+:*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
if (!addr)
return -EINVAL;
- /* Replace the old array with the new one, carefully: others can
- * be accessing it at the same time */
+ /*
+ * Replace the old array with the new one, carefully: others can
+ * be accessing it at the same time.
+ */
new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1),
GFP_KERNEL);
if (!new)
/* Now put new one in place. */
rcu_assign_pointer(lg->eventfds, new);
- /* We're not in a big hurry. Wait until noone's looking at old
- * version, then delete it. */
+ /*
+ * We're not in a big hurry. Wait until noone's looking at old
+ * version, then delete it.
+ */
synchronize_rcu();
kfree(old);
return err;
}
-/*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
- * number to /dev/lguest. */
+/*L:050
+ * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
+ * number to /dev/lguest.
+ */
static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
{
unsigned long irq;
return 0;
}
-/*L:040 Once our Guest is initialized, the Launcher makes it run by reading
- * from /dev/lguest. */
+/*L:040
+ * Once our Guest is initialized, the Launcher makes it run by reading
+ * from /dev/lguest.
+ */
static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
{
struct lguest *lg = file->private_data;
return len;
}
- /* If we returned from read() last time because the Guest sent I/O,
- * clear the flag. */
+ /*
+ * If we returned from read() last time because the Guest sent I/O,
+ * clear the flag.
+ */
if (cpu->pending_notify)
cpu->pending_notify = 0;
return run_guest(cpu, (unsigned long __user *)user);
}
-/*L:025 This actually initializes a CPU. For the moment, a Guest is only
- * uniprocessor, so "id" is always 0. */
+/*L:025
+ * This actually initializes a CPU. For the moment, a Guest is only
+ * uniprocessor, so "id" is always 0.
+ */
static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
{
/* We have a limited number the number of CPUs in the lguest struct. */
/* Each CPU has a timer it can set. */
init_clockdev(cpu);
- /* We need a complete page for the Guest registers: they are accessible
- * to the Guest and we can only grant it access to whole pages. */
+ /*
+ * We need a complete page for the Guest registers: they are accessible
+ * to the Guest and we can only grant it access to whole pages.
+ */
cpu->regs_page = get_zeroed_page(GFP_KERNEL);
if (!cpu->regs_page)
return -ENOMEM;
/* We actually put the registers at the bottom of the page. */
cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
- /* Now we initialize the Guest's registers, handing it the start
- * address. */
+ /*
+ * Now we initialize the Guest's registers, handing it the start
+ * address.
+ */
lguest_arch_setup_regs(cpu, start_ip);
- /* We keep a pointer to the Launcher task (ie. current task) for when
- * other Guests want to wake this one (eg. console input). */
+ /*
+ * We keep a pointer to the Launcher task (ie. current task) for when
+ * other Guests want to wake this one (eg. console input).
+ */
cpu->tsk = current;
- /* We need to keep a pointer to the Launcher's memory map, because if
+ /*
+ * We need to keep a pointer to the Launcher's memory map, because if
* the Launcher dies we need to clean it up. If we don't keep a
- * reference, it is destroyed before close() is called. */
+ * reference, it is destroyed before close() is called.
+ */
cpu->mm = get_task_mm(cpu->tsk);
- /* We remember which CPU's pages this Guest used last, for optimization
- * when the same Guest runs on the same CPU twice. */
+ /*
+ * We remember which CPU's pages this Guest used last, for optimization
+ * when the same Guest runs on the same CPU twice.
+ */
cpu->last_pages = NULL;
/* No error == success. */
return 0;
}
-/*L:020 The initialization write supplies 3 pointer sized (32 or 64 bit)
- * values (in addition to the LHREQ_INITIALIZE value). These are:
+/*L:020
+ * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in
+ * addition to the LHREQ_INITIALIZE value). These are:
*
* base: The start of the Guest-physical memory inside the Launcher memory.
*
*/
static int initialize(struct file *file, const unsigned long __user *input)
{
- /* "struct lguest" contains everything we (the Host) know about a
- * Guest. */
+ /* "struct lguest" contains all we (the Host) know about a Guest. */
struct lguest *lg;
int err;
unsigned long args[3];
- /* We grab the Big Lguest lock, which protects against multiple
- * simultaneous initializations. */
+ /*
+ * We grab the Big Lguest lock, which protects against multiple
+ * simultaneous initializations.
+ */
mutex_lock(&lguest_lock);
/* You can't initialize twice! Close the device and start again... */
if (file->private_data) {
if (err)
goto free_eventfds;
- /* Initialize the Guest's shadow page tables, using the toplevel
- * address the Launcher gave us. This allocates memory, so can fail. */
+ /*
+ * Initialize the Guest's shadow page tables, using the toplevel
+ * address the Launcher gave us. This allocates memory, so can fail.
+ */
err = init_guest_pagetable(lg);
if (err)
goto free_regs;
return err;
}
-/*L:010 The first operation the Launcher does must be a write. All writes
+/*L:010
+ * The first operation the Launcher does must be a write. All writes
* start with an unsigned long number: for the first write this must be
* LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
* writes of other values to send interrupts.
* Note that we overload the "offset" in the /dev/lguest file to indicate what
* CPU number we're dealing with. Currently this is always 0, since we only
* support uniprocessor Guests, but you can see the beginnings of SMP support
- * here. */
+ * here.
+ */
static ssize_t write(struct file *file, const char __user *in,
size_t size, loff_t *off)
{
- /* Once the Guest is initialized, we hold the "struct lguest" in the
- * file private data. */
+ /*
+ * Once the Guest is initialized, we hold the "struct lguest" in the
+ * file private data.
+ */
struct lguest *lg = file->private_data;
const unsigned long __user *input = (const unsigned long __user *)in;
unsigned long req;
}
}
-/*L:060 The final piece of interface code is the close() routine. It reverses
+/*L:060
+ * The final piece of interface code is the close() routine. It reverses
* everything done in initialize(). This is usually called because the
* Launcher exited.
*
* Note that the close routine returns 0 or a negative error number: it can't
* really fail, but it can whine. I blame Sun for this wart, and K&R C for
- * letting them do it. :*/
+ * letting them do it.
+:*/
static int close(struct inode *inode, struct file *file)
{
struct lguest *lg = file->private_data;
if (!lg)
return 0;
- /* We need the big lock, to protect from inter-guest I/O and other
- * Launchers initializing guests. */
+ /*
+ * We need the big lock, to protect from inter-guest I/O and other
+ * Launchers initializing guests.
+ */
mutex_lock(&lguest_lock);
/* Free up the shadow page tables for the Guest. */
hrtimer_cancel(&lg->cpus[i].hrt);
/* We can free up the register page we allocated. */
free_page(lg->cpus[i].regs_page);
- /* Now all the memory cleanups are done, it's safe to release
- * the Launcher's memory management structure. */
+ /*
+ * Now all the memory cleanups are done, it's safe to release
+ * the Launcher's memory management structure.
+ */
mmput(lg->cpus[i].mm);
}
eventfd_ctx_put(lg->eventfds->map[i].event);
kfree(lg->eventfds);
- /* If lg->dead doesn't contain an error code it will be NULL or a
- * kmalloc()ed string, either of which is ok to hand to kfree(). */
+ /*
+ * If lg->dead doesn't contain an error code it will be NULL or a
+ * kmalloc()ed string, either of which is ok to hand to kfree().
+ */
if (!IS_ERR(lg->dead))
kfree(lg->dead);
/* Free the memory allocated to the lguest_struct */
*
* We begin our understanding with the Host kernel interface which the Launcher
* uses: reading and writing a character device called /dev/lguest. All the
- * work happens in the read(), write() and close() routines: */
+ * work happens in the read(), write() and close() routines:
+ */
static struct file_operations lguest_fops = {
.owner = THIS_MODULE,
.release = close,
.read = read,
};
-/* This is a textbook example of a "misc" character device. Populate a "struct
- * miscdevice" and register it with misc_register(). */
+/*
+ * This is a textbook example of a "misc" character device. Populate a "struct
+ * miscdevice" and register it with misc_register().
+ */
static struct miscdevice lguest_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "lguest",
-/*P:700 The pagetable code, on the other hand, still shows the scars of
+/*P:700
+ * The pagetable code, on the other hand, still shows the scars of
* previous encounters. It's functional, and as neat as it can be in the
* circumstances, but be wary, for these things are subtle and break easily.
* The Guest provides a virtual to physical mapping, but we can neither trust
* it nor use it: we verify and convert it here then point the CPU to the
- * converted Guest pages when running the Guest. :*/
+ * converted Guest pages when running the Guest.
+:*/
/* Copyright (C) Rusty Russell IBM Corporation 2006.
* GPL v2 and any later version */
#include <asm/bootparam.h>
#include "lg.h"
-/*M:008 We hold reference to pages, which prevents them from being swapped.
+/*M:008
+ * We hold reference to pages, which prevents them from being swapped.
* It'd be nice to have a callback in the "struct mm_struct" when Linux wants
* to swap out. If we had this, and a shrinker callback to trim PTE pages, we
- * could probably consider launching Guests as non-root. :*/
+ * could probably consider launching Guests as non-root.
+:*/
/*H:300
* The Page Table Code
* (v) Flushing (throwing away) page tables,
* (vi) Mapping the Switcher when the Guest is about to run,
* (vii) Setting up the page tables initially.
- :*/
+:*/
-
-/* 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is
+/*
+ * 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is
* conveniently placed at the top 4MB, so it uses a separate, complete PTE
- * page. */
+ * page.
+ */
#define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1)
-/* For PAE we need the PMD index as well. We use the last 2MB, so we
- * will need the last pmd entry of the last pmd page. */
+/*
+ * For PAE we need the PMD index as well. We use the last 2MB, so we
+ * will need the last pmd entry of the last pmd page.
+ */
#ifdef CONFIG_X86_PAE
#define SWITCHER_PMD_INDEX (PTRS_PER_PMD - 1)
#define RESERVE_MEM 2U
#define CHECK_GPGD_MASK _PAGE_TABLE
#endif
-/* We actually need a separate PTE page for each CPU. Remember that after the
+/*
+ * We actually need a separate PTE page for each CPU. Remember that after the
* Switcher code itself comes two pages for each CPU, and we don't want this
- * CPU's guest to see the pages of any other CPU. */
+ * CPU's guest to see the pages of any other CPU.
+ */
static DEFINE_PER_CPU(pte_t *, switcher_pte_pages);
#define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu)
-/*H:320 The page table code is curly enough to need helper functions to keep it
+/*H:320
+ * The page table code is curly enough to need helper functions to keep it
* clear and clean.
*
* There are two functions which return pointers to the shadow (aka "real")
* spgd_addr() takes the virtual address and returns a pointer to the top-level
* page directory entry (PGD) for that address. Since we keep track of several
* page tables, the "i" argument tells us which one we're interested in (it's
- * usually the current one). */
+ * usually the current one).
+ */
static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr)
{
unsigned int index = pgd_index(vaddr);
}
#ifdef CONFIG_X86_PAE
-/* This routine then takes the PGD entry given above, which contains the
+/*
+ * This routine then takes the PGD entry given above, which contains the
* address of the PMD page. It then returns a pointer to the PMD entry for the
- * given address. */
+ * given address.
+ */
static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
{
unsigned int index = pmd_index(vaddr);
}
#endif
-/* This routine then takes the page directory entry returned above, which
+/*
+ * This routine then takes the page directory entry returned above, which
* contains the address of the page table entry (PTE) page. It then returns a
- * pointer to the PTE entry for the given address. */
+ * pointer to the PTE entry for the given address.
+ */
static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
{
#ifdef CONFIG_X86_PAE
return &page[pte_index(vaddr)];
}
-/* These two functions just like the above two, except they access the Guest
- * page tables. Hence they return a Guest address. */
+/*
+ * These two functions just like the above two, except they access the Guest
+ * page tables. Hence they return a Guest address.
+ */
static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr)
{
unsigned int index = vaddr >> (PGDIR_SHIFT);
#endif
/*:*/
-/*M:014 get_pfn is slow: we could probably try to grab batches of pages here as
- * an optimization (ie. pre-faulting). :*/
+/*M:014
+ * get_pfn is slow: we could probably try to grab batches of pages here as
+ * an optimization (ie. pre-faulting).
+:*/
-/*H:350 This routine takes a page number given by the Guest and converts it to
+/*H:350
+ * This routine takes a page number given by the Guest and converts it to
* an actual, physical page number. It can fail for several reasons: the
* virtual address might not be mapped by the Launcher, the write flag is set
* and the page is read-only, or the write flag was set and the page was
* shared so had to be copied, but we ran out of memory.
*
* This holds a reference to the page, so release_pte() is careful to put that
- * back. */
+ * back.
+ */
static unsigned long get_pfn(unsigned long virtpfn, int write)
{
struct page *page;
return -1UL;
}
-/*H:340 Converting a Guest page table entry to a shadow (ie. real) page table
+/*H:340
+ * Converting a Guest page table entry to a shadow (ie. real) page table
* entry can be a little tricky. The flags are (almost) the same, but the
* Guest PTE contains a virtual page number: the CPU needs the real page
- * number. */
+ * number.
+ */
static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write)
{
unsigned long pfn, base, flags;
- /* The Guest sets the global flag, because it thinks that it is using
+ /*
+ * The Guest sets the global flag, because it thinks that it is using
* PGE. We only told it to use PGE so it would tell us whether it was
* flushing a kernel mapping or a userspace mapping. We don't actually
- * use the global bit, so throw it away. */
+ * use the global bit, so throw it away.
+ */
flags = (pte_flags(gpte) & ~_PAGE_GLOBAL);
/* The Guest's pages are offset inside the Launcher. */
base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE;
- /* We need a temporary "unsigned long" variable to hold the answer from
+ /*
+ * We need a temporary "unsigned long" variable to hold the answer from
* get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't
* fit in spte.pfn. get_pfn() finds the real physical number of the
- * page, given the virtual number. */
+ * page, given the virtual number.
+ */
pfn = get_pfn(base + pte_pfn(gpte), write);
if (pfn == -1UL) {
kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte));
- /* When we destroy the Guest, we'll go through the shadow page
+ /*
+ * When we destroy the Guest, we'll go through the shadow page
* tables and release_pte() them. Make sure we don't think
- * this one is valid! */
+ * this one is valid!
+ */
flags = 0;
}
/* Now we assemble our shadow PTE from the page number and flags. */
/*H:460 And to complete the chain, release_pte() looks like this: */
static void release_pte(pte_t pte)
{
- /* Remember that get_user_pages_fast() took a reference to the page, in
- * get_pfn()? We have to put it back now. */
+ /*
+ * Remember that get_user_pages_fast() took a reference to the page, in
+ * get_pfn()? We have to put it back now.
+ */
if (pte_flags(pte) & _PAGE_PRESENT)
put_page(pte_page(pte));
}
* and return to the Guest without it knowing.
*
* If we fixed up the fault (ie. we mapped the address), this routine returns
- * true. Otherwise, it was a real fault and we need to tell the Guest. */
+ * true. Otherwise, it was a real fault and we need to tell the Guest.
+ */
bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
{
pgd_t gpgd;
if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) {
/* No shadow entry: allocate a new shadow PTE page. */
unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
- /* This is not really the Guest's fault, but killing it is
- * simple for this corner case. */
+ /*
+ * This is not really the Guest's fault, but killing it is
+ * simple for this corner case.
+ */
if (!ptepage) {
kill_guest(cpu, "out of memory allocating pte page");
return false;
}
/* We check that the Guest pgd is OK. */
check_gpgd(cpu, gpgd);
- /* And we copy the flags to the shadow PGD entry. The page
- * number in the shadow PGD is the page we just allocated. */
+ /*
+ * And we copy the flags to the shadow PGD entry. The page
+ * number in the shadow PGD is the page we just allocated.
+ */
set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd)));
}
#ifdef CONFIG_X86_PAE
gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
- /* middle level not present? We can't map it in. */
+ /* Middle level not present? We can't map it in. */
if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
return false;
/* No shadow entry: allocate a new shadow PTE page. */
unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
- /* This is not really the Guest's fault, but killing it is
- * simple for this corner case. */
+ /*
+ * This is not really the Guest's fault, but killing it is
+ * simple for this corner case.
+ */
if (!ptepage) {
kill_guest(cpu, "out of memory allocating pte page");
return false;
/* We check that the Guest pmd is OK. */
check_gpmd(cpu, gpmd);
- /* And we copy the flags to the shadow PMD entry. The page
- * number in the shadow PMD is the page we just allocated. */
+ /*
+ * And we copy the flags to the shadow PMD entry. The page
+ * number in the shadow PMD is the page we just allocated.
+ */
native_set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd)));
}
- /* OK, now we look at the lower level in the Guest page table: keep its
- * address, because we might update it later. */
+ /*
+ * OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later.
+ */
gpte_ptr = gpte_addr(cpu, gpmd, vaddr);
#else
- /* OK, now we look at the lower level in the Guest page table: keep its
- * address, because we might update it later. */
+ /*
+ * OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later.
+ */
gpte_ptr = gpte_addr(cpu, gpgd, vaddr);
#endif
gpte = lgread(cpu, gpte_ptr, pte_t);
if (!(pte_flags(gpte) & _PAGE_PRESENT))
return false;
- /* Check they're not trying to write to a page the Guest wants
- * read-only (bit 2 of errcode == write). */
+ /*
+ * Check they're not trying to write to a page the Guest wants
+ * read-only (bit 2 of errcode == write).
+ */
if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW))
return false;
if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER))
return false;
- /* Check that the Guest PTE flags are OK, and the page number is below
- * the pfn_limit (ie. not mapping the Launcher binary). */
+ /*
+ * Check that the Guest PTE flags are OK, and the page number is below
+ * the pfn_limit (ie. not mapping the Launcher binary).
+ */
check_gpte(cpu, gpte);
/* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */
/* Get the pointer to the shadow PTE entry we're going to set. */
spte = spte_addr(cpu, *spgd, vaddr);
- /* If there was a valid shadow PTE entry here before, we release it.
- * This can happen with a write to a previously read-only entry. */
+
+ /*
+ * If there was a valid shadow PTE entry here before, we release it.
+ * This can happen with a write to a previously read-only entry.
+ */
release_pte(*spte);
- /* If this is a write, we insist that the Guest page is writable (the
- * final arg to gpte_to_spte()). */
+ /*
+ * If this is a write, we insist that the Guest page is writable (the
+ * final arg to gpte_to_spte()).
+ */
if (pte_dirty(gpte))
*spte = gpte_to_spte(cpu, gpte, 1);
else
- /* If this is a read, don't set the "writable" bit in the page
+ /*
+ * If this is a read, don't set the "writable" bit in the page
* table entry, even if the Guest says it's writable. That way
* we will come back here when a write does actually occur, so
- * we can update the Guest's _PAGE_DIRTY flag. */
+ * we can update the Guest's _PAGE_DIRTY flag.
+ */
native_set_pte(spte, gpte_to_spte(cpu, pte_wrprotect(gpte), 0));
- /* Finally, we write the Guest PTE entry back: we've set the
- * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */
+ /*
+ * Finally, we write the Guest PTE entry back: we've set the
+ * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags.
+ */
lgwrite(cpu, gpte_ptr, pte_t, gpte);
- /* The fault is fixed, the page table is populated, the mapping
+ /*
+ * The fault is fixed, the page table is populated, the mapping
* manipulated, the result returned and the code complete. A small
* delay and a trace of alliteration are the only indications the Guest
- * has that a page fault occurred at all. */
+ * has that a page fault occurred at all.
+ */
return true;
}
* mapped, so it's overkill.
*
* This is a quick version which answers the question: is this virtual address
- * mapped by the shadow page tables, and is it writable? */
+ * mapped by the shadow page tables, and is it writable?
+ */
static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
{
pgd_t *spgd;
return false;
#endif
- /* Check the flags on the pte entry itself: it must be present and
- * writable. */
+ /*
+ * Check the flags on the pte entry itself: it must be present and
+ * writable.
+ */
flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr)));
return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
}
-/* So, when pin_stack_pages() asks us to pin a page, we check if it's already
+/*
+ * So, when pin_stack_pages() asks us to pin a page, we check if it's already
* in the page tables, and if not, we call demand_page() with error code 2
- * (meaning "write"). */
+ * (meaning "write").
+ */
void pin_page(struct lg_cpu *cpu, unsigned long vaddr)
{
if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2))
/* If the entry's not present, there's nothing to release. */
if (pgd_flags(*spgd) & _PAGE_PRESENT) {
unsigned int i;
- /* Converting the pfn to find the actual PTE page is easy: turn
+ /*
+ * Converting the pfn to find the actual PTE page is easy: turn
* the page number into a physical address, then convert to a
- * virtual address (easy for kernel pages like this one). */
+ * virtual address (easy for kernel pages like this one).
+ */
pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
/* For each entry in the page, we might need to release it. */
for (i = 0; i < PTRS_PER_PTE; i++)
}
}
#endif
-/*H:445 We saw flush_user_mappings() twice: once from the flush_user_mappings()
+
+/*H:445
+ * We saw flush_user_mappings() twice: once from the flush_user_mappings()
* hypercall and once in new_pgdir() when we re-used a top-level pgdir page.
- * It simply releases every PTE page from 0 up to the Guest's kernel address. */
+ * It simply releases every PTE page from 0 up to the Guest's kernel address.
+ */
static void flush_user_mappings(struct lguest *lg, int idx)
{
unsigned int i;
release_pgd(lg->pgdirs[idx].pgdir + i);
}
-/*H:440 (v) Flushing (throwing away) page tables,
+/*H:440
+ * (v) Flushing (throwing away) page tables,
*
* The Guest has a hypercall to throw away the page tables: it's used when a
- * large number of mappings have been changed. */
+ * large number of mappings have been changed.
+ */
void guest_pagetable_flush_user(struct lg_cpu *cpu)
{
/* Drop the userspace part of the current page table. */
return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
}
-/* We keep several page tables. This is a simple routine to find the page
+/*
+ * We keep several page tables. This is a simple routine to find the page
* table (if any) corresponding to this top-level address the Guest has given
- * us. */
+ * us.
+ */
static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable)
{
unsigned int i;
return i;
}
-/*H:435 And this is us, creating the new page directory. If we really do
+/*H:435
+ * And this is us, creating the new page directory. If we really do
* allocate a new one (and so the kernel parts are not there), we set
- * blank_pgdir. */
+ * blank_pgdir.
+ */
static unsigned int new_pgdir(struct lg_cpu *cpu,
unsigned long gpgdir,
int *blank_pgdir)
pmd_t *pmd_table;
#endif
- /* We pick one entry at random to throw out. Choosing the Least
- * Recently Used might be better, but this is easy. */
+ /*
+ * We pick one entry at random to throw out. Choosing the Least
+ * Recently Used might be better, but this is easy.
+ */
next = random32() % ARRAY_SIZE(cpu->lg->pgdirs);
/* If it's never been allocated at all before, try now. */
if (!cpu->lg->pgdirs[next].pgdir) {
next = cpu->cpu_pgd;
else {
#ifdef CONFIG_X86_PAE
- /* In PAE mode, allocate a pmd page and populate the
- * last pgd entry. */
+ /*
+ * In PAE mode, allocate a pmd page and populate the
+ * last pgd entry.
+ */
pmd_table = (pmd_t *)get_zeroed_page(GFP_KERNEL);
if (!pmd_table) {
free_page((long)cpu->lg->pgdirs[next].pgdir);
set_pgd(cpu->lg->pgdirs[next].pgdir +
SWITCHER_PGD_INDEX,
__pgd(__pa(pmd_table) | _PAGE_PRESENT));
- /* This is a blank page, so there are no kernel
- * mappings: caller must map the stack! */
+ /*
+ * This is a blank page, so there are no kernel
+ * mappings: caller must map the stack!
+ */
*blank_pgdir = 1;
}
#else
return next;
}
-/*H:430 (iv) Switching page tables
+/*H:430
+ * (iv) Switching page tables
*
* Now we've seen all the page table setting and manipulation, let's see
* what happens when the Guest changes page tables (ie. changes the top-level
- * pgdir). This occurs on almost every context switch. */
+ * pgdir). This occurs on almost every context switch.
+ */
void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable)
{
int newpgdir, repin = 0;
/* Look to see if we have this one already. */
newpgdir = find_pgdir(cpu->lg, pgtable);
- /* If not, we allocate or mug an existing one: if it's a fresh one,
- * repin gets set to 1. */
+ /*
+ * If not, we allocate or mug an existing one: if it's a fresh one,
+ * repin gets set to 1.
+ */
if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs))
newpgdir = new_pgdir(cpu, pgtable, &repin);
/* Change the current pgd index to the new one. */
pin_stack_pages(cpu);
}
-/*H:470 Finally, a routine which throws away everything: all PGD entries in all
+/*H:470
+ * Finally, a routine which throws away everything: all PGD entries in all
* the shadow page tables, including the Guest's kernel mappings. This is used
- * when we destroy the Guest. */
+ * when we destroy the Guest.
+ */
static void release_all_pagetables(struct lguest *lg)
{
unsigned int i, j;
spgd = lg->pgdirs[i].pgdir + SWITCHER_PGD_INDEX;
pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
- /* And release the pmd entries of that pmd page,
- * except for the switcher pmd. */
+ /*
+ * And release the pmd entries of that pmd page,
+ * except for the switcher pmd.
+ */
for (k = 0; k < SWITCHER_PMD_INDEX; k++)
release_pmd(&pmdpage[k]);
#endif
}
}
-/* We also throw away everything when a Guest tells us it's changed a kernel
+/*
+ * We also throw away everything when a Guest tells us it's changed a kernel
* mapping. Since kernel mappings are in every page table, it's easiest to
* throw them all away. This traps the Guest in amber for a while as
- * everything faults back in, but it's rare. */
+ * everything faults back in, but it's rare.
+ */
void guest_pagetable_clear_all(struct lg_cpu *cpu)
{
release_all_pagetables(cpu->lg);
pin_stack_pages(cpu);
}
/*:*/
-/*M:009 Since we throw away all mappings when a kernel mapping changes, our
+
+/*M:009
+ * Since we throw away all mappings when a kernel mapping changes, our
* performance sucks for guests using highmem. In fact, a guest with
* PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is
* usually slower than a Guest with less memory.
*
* This, of course, cannot be fixed. It would take some kind of... well, I
- * don't know, but the term "puissant code-fu" comes to mind. :*/
+ * don't know, but the term "puissant code-fu" comes to mind.
+:*/
-/*H:420 This is the routine which actually sets the page table entry for then
+/*H:420
+ * This is the routine which actually sets the page table entry for then
* "idx"'th shadow page table.
*
* Normally, we can just throw out the old entry and replace it with 0: if they
spmd = spmd_addr(cpu, *spgd, vaddr);
if (pmd_flags(*spmd) & _PAGE_PRESENT) {
#endif
- /* Otherwise, we start by releasing
- * the existing entry. */
+ /* Otherwise, start by releasing the existing entry. */
pte_t *spte = spte_addr(cpu, *spgd, vaddr);
release_pte(*spte);
- /* If they're setting this entry as dirty or accessed,
- * we might as well put that entry they've given us
- * in now. This shaves 10% off a
- * copy-on-write micro-benchmark. */
+ /*
+ * If they're setting this entry as dirty or accessed,
+ * we might as well put that entry they've given us in
+ * now. This shaves 10% off a copy-on-write
+ * micro-benchmark.
+ */
if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
check_gpte(cpu, gpte);
native_set_pte(spte,
gpte_to_spte(cpu, gpte,
pte_flags(gpte) & _PAGE_DIRTY));
- } else
- /* Otherwise kill it and we can demand_page()
- * it in later. */
+ } else {
+ /*
+ * Otherwise kill it and we can demand_page()
+ * it in later.
+ */
native_set_pte(spte, __pte(0));
+ }
#ifdef CONFIG_X86_PAE
}
#endif
}
}
-/*H:410 Updating a PTE entry is a little trickier.
+/*H:410
+ * Updating a PTE entry is a little trickier.
*
* We keep track of several different page tables (the Guest uses one for each
* process, so it makes sense to cache at least a few). Each of these have
* all the page tables, not just the current one. This is rare.
*
* The benefit is that when we have to track a new page table, we can keep all
- * the kernel mappings. This speeds up context switch immensely. */
+ * the kernel mappings. This speeds up context switch immensely.
+ */
void guest_set_pte(struct lg_cpu *cpu,
unsigned long gpgdir, unsigned long vaddr, pte_t gpte)
{
- /* Kernel mappings must be changed on all top levels. Slow, but doesn't
- * happen often. */
+ /*
+ * Kernel mappings must be changed on all top levels. Slow, but doesn't
+ * happen often.
+ */
if (vaddr >= cpu->lg->kernel_address) {
unsigned int i;
for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++)
}
#endif
-/* Once we know how much memory we have we can construct simple identity
- * (which set virtual == physical) and linear mappings
- * which will get the Guest far enough into the boot to create its own.
+/*
+ * Once we know how much memory we have we can construct simple identity (which
+ * set virtual == physical) and linear mappings which will get the Guest far
+ * enough into the boot to create its own.
*
* We lay them out of the way, just below the initrd (which is why we need to
- * know its size here). */
+ * know its size here).
+ */
static unsigned long setup_pagetables(struct lguest *lg,
unsigned long mem,
unsigned long initrd_size)
unsigned int phys_linear;
#endif
- /* We have mapped_pages frames to map, so we need
- * linear_pages page tables to map them. */
+ /*
+ * We have mapped_pages frames to map, so we need linear_pages page
+ * tables to map them.
+ */
mapped_pages = mem / PAGE_SIZE;
linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE;
#ifdef CONFIG_X86_PAE
pmds = (void *)linear - PAGE_SIZE;
#endif
- /* Linear mapping is easy: put every page's address into the
- * mapping in order. */
+ /*
+ * Linear mapping is easy: put every page's address into the
+ * mapping in order.
+ */
for (i = 0; i < mapped_pages; i++) {
pte_t pte;
pte = pfn_pte(i, __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_USER));
return -EFAULT;
}
- /* The top level points to the linear page table pages above.
- * We setup the identity and linear mappings here. */
+ /*
+ * The top level points to the linear page table pages above.
+ * We setup the identity and linear mappings here.
+ */
#ifdef CONFIG_X86_PAE
for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD;
i += PTRS_PER_PTE, j++) {
}
#endif
- /* We return the top level (guest-physical) address: remember where
- * this is. */
+ /*
+ * We return the top level (guest-physical) address: remember where
+ * this is.
+ */
return (unsigned long)pgdir - mem_base;
}
-/*H:500 (vii) Setting up the page tables initially.
+/*H:500
+ * (vii) Setting up the page tables initially.
*
* When a Guest is first created, the Launcher tells us where the toplevel of
- * its first page table is. We set some things up here: */
+ * its first page table is. We set some things up here:
+ */
int init_guest_pagetable(struct lguest *lg)
{
u64 mem;
pgd_t *pgd;
pmd_t *pmd_table;
#endif
- /* Get the Guest memory size and the ramdisk size from the boot header
- * located at lg->mem_base (Guest address 0). */
+ /*
+ * Get the Guest memory size and the ramdisk size from the boot header
+ * located at lg->mem_base (Guest address 0).
+ */
if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem))
|| get_user(initrd_size, &boot->hdr.ramdisk_size))
return -EFAULT;
- /* We start on the first shadow page table, and give it a blank PGD
- * page. */
+ /*
+ * We start on the first shadow page table, and give it a blank PGD
+ * page.
+ */
lg->pgdirs[0].gpgdir = setup_pagetables(lg, mem, initrd_size);
if (IS_ERR_VALUE(lg->pgdirs[0].gpgdir))
return lg->pgdirs[0].gpgdir;
/* We get the kernel address: above this is all kernel memory. */
if (get_user(cpu->lg->kernel_address,
&cpu->lg->lguest_data->kernel_address)
- /* We tell the Guest that it can't use the top 2 or 4 MB
- * of virtual addresses used by the Switcher. */
+ /*
+ * We tell the Guest that it can't use the top 2 or 4 MB
+ * of virtual addresses used by the Switcher.
+ */
|| put_user(RESERVE_MEM * 1024 * 1024,
&cpu->lg->lguest_data->reserve_mem)
|| put_user(cpu->lg->pgdirs[0].gpgdir,
&cpu->lg->lguest_data->pgdir))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
- /* In flush_user_mappings() we loop from 0 to
+ /*
+ * In flush_user_mappings() we loop from 0 to
* "pgd_index(lg->kernel_address)". This assumes it won't hit the
- * Switcher mappings, so check that now. */
+ * Switcher mappings, so check that now.
+ */
#ifdef CONFIG_X86_PAE
if (pgd_index(cpu->lg->kernel_address) == SWITCHER_PGD_INDEX &&
pmd_index(cpu->lg->kernel_address) == SWITCHER_PMD_INDEX)
free_page((long)lg->pgdirs[i].pgdir);
}
-/*H:480 (vi) Mapping the Switcher when the Guest is about to run.
+/*H:480
+ * (vi) Mapping the Switcher when the Guest is about to run.
*
* The Switcher and the two pages for this CPU need to be visible in the
* Guest (and not the pages for other CPUs). We have the appropriate PTE pages
* for each CPU already set up, we just need to hook them in now we know which
- * Guest is about to run on this CPU. */
+ * Guest is about to run on this CPU.
+ */
void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
{
pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages);
#else
pgd_t switcher_pgd;
- /* Make the last PGD entry for this Guest point to the Switcher's PTE
- * page for this CPU (with appropriate flags). */
+ /*
+ * Make the last PGD entry for this Guest point to the Switcher's PTE
+ * page for this CPU (with appropriate flags).
+ */
switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL_EXEC);
cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;
#endif
- /* We also change the Switcher PTE page. When we're running the Guest,
+ /*
+ * We also change the Switcher PTE page. When we're running the Guest,
* we want the Guest's "regs" page to appear where the first Switcher
* page for this CPU is. This is an optimization: when the Switcher
* saves the Guest registers, it saves them into the first page of this
* CPU's "struct lguest_pages": if we make sure the Guest's register
* page is already mapped there, we don't have to copy them out
- * again. */
+ * again.
+ */
pfn = __pa(cpu->regs_page) >> PAGE_SHIFT;
native_set_pte(®s_pte, pfn_pte(pfn, PAGE_KERNEL));
native_set_pte(&switcher_pte_page[pte_index((unsigned long)pages)],
free_page((long)switcher_pte_page(i));
}
-/*H:520 Setting up the Switcher PTE page for given CPU is fairly easy, given
+/*H:520
+ * Setting up the Switcher PTE page for given CPU is fairly easy, given
* the CPU number and the "struct page"s for the Switcher code itself.
*
- * Currently the Switcher is less than a page long, so "pages" is always 1. */
+ * Currently the Switcher is less than a page long, so "pages" is always 1.
+ */
static __init void populate_switcher_pte_page(unsigned int cpu,
struct page *switcher_page[],
unsigned int pages)
native_set_pte(&pte[i], pfn_pte(page_to_pfn(switcher_page[i]),
__pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW)));
- /* The second page contains the "struct lguest_ro_state", and is
- * read-only. */
+ /*
+ * The second page contains the "struct lguest_ro_state", and is
+ * read-only.
+ */
native_set_pte(&pte[i+1], pfn_pte(page_to_pfn(switcher_page[i+1]),
__pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)));
}
-/* We've made it through the page table code. Perhaps our tired brains are
+/*
+ * We've made it through the page table code. Perhaps our tired brains are
* still processing the details, or perhaps we're simply glad it's over.
*
* If nothing else, note that all this complexity in juggling shadow page tables
* uses exotic direct Guest pagetable manipulation, and why both Intel and AMD
* have implemented shadow page table support directly into hardware.
*
- * There is just one file remaining in the Host. */
+ * There is just one file remaining in the Host.
+ */
-/*H:510 At boot or module load time, init_pagetables() allocates and populates
- * the Switcher PTE page for each CPU. */
+/*H:510
+ * At boot or module load time, init_pagetables() allocates and populates
+ * the Switcher PTE page for each CPU.
+ */
__init int init_pagetables(struct page **switcher_page, unsigned int pages)
{
unsigned int i;
-/*P:600 The x86 architecture has segments, which involve a table of descriptors
+/*P:600
+ * The x86 architecture has segments, which involve a table of descriptors
* which can be used to do funky things with virtual address interpretation.
* We originally used to use segments so the Guest couldn't alter the
* Guest<->Host Switcher, and then we had to trim Guest segments, and restore
*
* In these modern times, the segment handling code consists of simple sanity
* checks, and the worst you'll experience reading this code is butterfly-rash
- * from frolicking through its parklike serenity. :*/
+ * from frolicking through its parklike serenity.
+:*/
#include "lg.h"
/*H:600
* begin.
*/
-/* There are several entries we don't let the Guest set. The TSS entry is the
+/*
+ * There are several entries we don't let the Guest set. The TSS entry is the
* "Task State Segment" which controls all kinds of delicate things. The
* LGUEST_CS and LGUEST_DS entries are reserved for the Switcher, and the
- * the Guest can't be trusted to deal with double faults. */
+ * the Guest can't be trusted to deal with double faults.
+ */
static bool ignored_gdt(unsigned int num)
{
return (num == GDT_ENTRY_TSS
|| num == GDT_ENTRY_DOUBLEFAULT_TSS);
}
-/*H:630 Once the Guest gave us new GDT entries, we fix them up a little. We
+/*H:630
+ * Once the Guest gave us new GDT entries, we fix them up a little. We
* don't care if they're invalid: the worst that can happen is a General
* Protection Fault in the Switcher when it restores a Guest segment register
* which tries to use that entry. Then we kill the Guest for causing such a
- * mess: the message will be "unhandled trap 256". */
+ * mess: the message will be "unhandled trap 256".
+ */
static void fixup_gdt_table(struct lg_cpu *cpu, unsigned start, unsigned end)
{
unsigned int i;
for (i = start; i < end; i++) {
- /* We never copy these ones to real GDT, so we don't care what
- * they say */
+ /*
+ * We never copy these ones to real GDT, so we don't care what
+ * they say
+ */
if (ignored_gdt(i))
continue;
- /* Segment descriptors contain a privilege level: the Guest is
+ /*
+ * Segment descriptors contain a privilege level: the Guest is
* sometimes careless and leaves this as 0, even though it's
- * running at privilege level 1. If so, we fix it here. */
+ * running at privilege level 1. If so, we fix it here.
+ */
if ((cpu->arch.gdt[i].b & 0x00006000) == 0)
cpu->arch.gdt[i].b |= (GUEST_PL << 13);
- /* Each descriptor has an "accessed" bit. If we don't set it
+ /*
+ * Each descriptor has an "accessed" bit. If we don't set it
* now, the CPU will try to set it when the Guest first loads
* that entry into a segment register. But the GDT isn't
- * writable by the Guest, so bad things can happen. */
+ * writable by the Guest, so bad things can happen.
+ */
cpu->arch.gdt[i].b |= 0x00000100;
}
}
-/*H:610 Like the IDT, we never simply use the GDT the Guest gives us. We keep
+/*H:610
+ * Like the IDT, we never simply use the GDT the Guest gives us. We keep
* a GDT for each CPU, and copy across the Guest's entries each time we want to
* run the Guest on that CPU.
*
* This routine is called at boot or modprobe time for each CPU to set up the
* constant GDT entries: the ones which are the same no matter what Guest we're
- * running. */
+ * running.
+ */
void setup_default_gdt_entries(struct lguest_ro_state *state)
{
struct desc_struct *gdt = state->guest_gdt;
gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
- /* The TSS segment refers to the TSS entry for this particular CPU.
+ /*
+ * The TSS segment refers to the TSS entry for this particular CPU.
* Forgive the magic flags: the 0x8900 means the entry is Present, it's
* privilege level 0 Available 386 TSS system segment, and the 0x67
- * means Saturn is eclipsed by Mercury in the twelfth house. */
+ * means Saturn is eclipsed by Mercury in the twelfth house.
+ */
gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16);
gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000)
| ((tss >> 16) & 0x000000FF);
}
-/* This routine sets up the initial Guest GDT for booting. All entries start
- * as 0 (unusable). */
+/*
+ * This routine sets up the initial Guest GDT for booting. All entries start
+ * as 0 (unusable).
+ */
void setup_guest_gdt(struct lg_cpu *cpu)
{
- /* Start with full 0-4G segments... */
+ /*
+ * Start with full 0-4G segments...except the Guest is allowed to use
+ * them, so set the privilege level appropriately in the flags.
+ */
cpu->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT;
cpu->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT;
- /* ...except the Guest is allowed to use them, so set the privilege
- * level appropriately in the flags. */
cpu->arch.gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13);
cpu->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13);
}
-/*H:650 An optimization of copy_gdt(), for just the three "thead-local storage"
- * entries. */
+/*H:650
+ * An optimization of copy_gdt(), for just the three "thead-local storage"
+ * entries.
+ */
void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt)
{
unsigned int i;
gdt[i] = cpu->arch.gdt[i];
}
-/*H:640 When the Guest is run on a different CPU, or the GDT entries have
- * changed, copy_gdt() is called to copy the Guest's GDT entries across to this
- * CPU's GDT. */
+/*H:640
+ * When the Guest is run on a different CPU, or the GDT entries have changed,
+ * copy_gdt() is called to copy the Guest's GDT entries across to this CPU's
+ * GDT.
+ */
void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt)
{
unsigned int i;
- /* The default entries from setup_default_gdt_entries() are not
- * replaced. See ignored_gdt() above. */
+ /*
+ * The default entries from setup_default_gdt_entries() are not
+ * replaced. See ignored_gdt() above.
+ */
for (i = 0; i < GDT_ENTRIES; i++)
if (!ignored_gdt(i))
gdt[i] = cpu->arch.gdt[i];
}
-/*H:620 This is where the Guest asks us to load a new GDT entry
- * (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. */
+/*H:620
+ * This is where the Guest asks us to load a new GDT entry
+ * (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in.
+ */
void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi)
{
- /* We assume the Guest has the same number of GDT entries as the
- * Host, otherwise we'd have to dynamically allocate the Guest GDT. */
+ /*
+ * We assume the Guest has the same number of GDT entries as the
+ * Host, otherwise we'd have to dynamically allocate the Guest GDT.
+ */
if (num >= ARRAY_SIZE(cpu->arch.gdt))
kill_guest(cpu, "too many gdt entries %i", num);
cpu->arch.gdt[num].a = lo;
cpu->arch.gdt[num].b = hi;
fixup_gdt_table(cpu, num, num+1);
- /* Mark that the GDT changed so the core knows it has to copy it again,
- * even if the Guest is run on the same CPU. */
+ /*
+ * Mark that the GDT changed so the core knows it has to copy it again,
+ * even if the Guest is run on the same CPU.
+ */
cpu->changed |= CHANGED_GDT;
}
-/* This is the fast-track version for just changing the three TLS entries.
+/*
+ * This is the fast-track version for just changing the three TLS entries.
* Remember that this happens on every context switch, so it's worth
* optimizing. But wouldn't it be neater to have a single hypercall to cover
- * both cases? */
+ * both cases?
+ */
void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls)
{
struct desc_struct *tls = &cpu->arch.gdt[GDT_ENTRY_TLS_MIN];
/* Note that just the TLS entries have changed. */
cpu->changed |= CHANGED_GDT_TLS;
}
-/*:*/
/*H:660
* With this, we have finished the Host.
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
-/*P:450 This file contains the x86-specific lguest code. It used to be all
+/*P:450
+ * This file contains the x86-specific lguest code. It used to be all
* mixed in with drivers/lguest/core.c but several foolhardy code slashers
* wrestled most of the dependencies out to here in preparation for porting
* lguest to other architectures (see what I mean by foolhardy?).
*
* This also contains a couple of non-obvious setup and teardown pieces which
- * were implemented after days of debugging pain. :*/
+ * were implemented after days of debugging pain.
+:*/
#include <linux/kernel.h>
#include <linux/start_kernel.h>
#include <linux/string.h>
*/
static void copy_in_guest_info(struct lg_cpu *cpu, struct lguest_pages *pages)
{
- /* Copying all this data can be quite expensive. We usually run the
+ /*
+ * Copying all this data can be quite expensive. We usually run the
* same Guest we ran last time (and that Guest hasn't run anywhere else
* meanwhile). If that's not the case, we pretend everything in the
- * Guest has changed. */
+ * Guest has changed.
+ */
if (__get_cpu_var(last_cpu) != cpu || cpu->last_pages != pages) {
__get_cpu_var(last_cpu) = cpu;
cpu->last_pages = pages;
cpu->changed = CHANGED_ALL;
}
- /* These copies are pretty cheap, so we do them unconditionally: */
- /* Save the current Host top-level page directory. */
+ /*
+ * These copies are pretty cheap, so we do them unconditionally: */
+ /* Save the current Host top-level page directory.
+ */
pages->state.host_cr3 = __pa(current->mm->pgd);
- /* Set up the Guest's page tables to see this CPU's pages (and no
- * other CPU's pages). */
+ /*
+ * Set up the Guest's page tables to see this CPU's pages (and no
+ * other CPU's pages).
+ */
map_switcher_in_guest(cpu, pages);
- /* Set up the two "TSS" members which tell the CPU what stack to use
+ /*
+ * Set up the two "TSS" members which tell the CPU what stack to use
* for traps which do directly into the Guest (ie. traps at privilege
- * level 1). */
+ * level 1).
+ */
pages->state.guest_tss.sp1 = cpu->esp1;
pages->state.guest_tss.ss1 = cpu->ss1;
/* This is a dummy value we need for GCC's sake. */
unsigned int clobber;
- /* Copy the guest-specific information into this CPU's "struct
- * lguest_pages". */
+ /*
+ * Copy the guest-specific information into this CPU's "struct
+ * lguest_pages".
+ */
copy_in_guest_info(cpu, pages);
- /* Set the trap number to 256 (impossible value). If we fault while
+ /*
+ * Set the trap number to 256 (impossible value). If we fault while
* switching to the Guest (bad segment registers or bug), this will
- * cause us to abort the Guest. */
+ * cause us to abort the Guest.
+ */
cpu->regs->trapnum = 256;
- /* Now: we push the "eflags" register on the stack, then do an "lcall".
+ /*
+ * Now: we push the "eflags" register on the stack, then do an "lcall".
* This is how we change from using the kernel code segment to using
* the dedicated lguest code segment, as well as jumping into the
* Switcher.
*
* The lcall also pushes the old code segment (KERNEL_CS) onto the
* stack, then the address of this call. This stack layout happens to
- * exactly match the stack layout created by an interrupt... */
+ * exactly match the stack layout created by an interrupt...
+ */
asm volatile("pushf; lcall *lguest_entry"
- /* This is how we tell GCC that %eax ("a") and %ebx ("b")
- * are changed by this routine. The "=" means output. */
+ /*
+ * This is how we tell GCC that %eax ("a") and %ebx ("b")
+ * are changed by this routine. The "=" means output.
+ */
: "=a"(clobber), "=b"(clobber)
- /* %eax contains the pages pointer. ("0" refers to the
+ /*
+ * %eax contains the pages pointer. ("0" refers to the
* 0-th argument above, ie "a"). %ebx contains the
* physical address of the Guest's top-level page
- * directory. */
+ * directory.
+ */
: "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir))
- /* We tell gcc that all these registers could change,
+ /*
+ * We tell gcc that all these registers could change,
* which means we don't have to save and restore them in
- * the Switcher. */
+ * the Switcher.
+ */
: "memory", "%edx", "%ecx", "%edi", "%esi");
}
/*:*/
-/*M:002 There are hooks in the scheduler which we can register to tell when we
+/*M:002
+ * There are hooks in the scheduler which we can register to tell when we
* get kicked off the CPU (preempt_notifier_register()). This would allow us
* to lazily disable SYSENTER which would regain some performance, and should
* also simplify copy_in_guest_info(). Note that we'd still need to restore
*
* We could also try using this hooks for PGE, but that might be too expensive.
*
- * The hooks were designed for KVM, but we can also put them to good use. :*/
+ * The hooks were designed for KVM, but we can also put them to good use.
+:*/
-/*H:040 This is the i386-specific code to setup and run the Guest. Interrupts
- * are disabled: we own the CPU. */
+/*H:040
+ * This is the i386-specific code to setup and run the Guest. Interrupts
+ * are disabled: we own the CPU.
+ */
void lguest_arch_run_guest(struct lg_cpu *cpu)
{
- /* Remember the awfully-named TS bit? If the Guest has asked to set it
+ /*
+ * Remember the awfully-named TS bit? If the Guest has asked to set it
* we set it now, so we can trap and pass that trap to the Guest if it
- * uses the FPU. */
+ * uses the FPU.
+ */
if (cpu->ts)
unlazy_fpu(current);
- /* SYSENTER is an optimized way of doing system calls. We can't allow
+ /*
+ * SYSENTER is an optimized way of doing system calls. We can't allow
* it because it always jumps to privilege level 0. A normal Guest
* won't try it because we don't advertise it in CPUID, but a malicious
* Guest (or malicious Guest userspace program) could, so we tell the
- * CPU to disable it before running the Guest. */
+ * CPU to disable it before running the Guest.
+ */
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
- /* Now we actually run the Guest. It will return when something
+ /*
+ * Now we actually run the Guest. It will return when something
* interesting happens, and we can examine its registers to see what it
- * was doing. */
+ * was doing.
+ */
run_guest_once(cpu, lguest_pages(raw_smp_processor_id()));
- /* Note that the "regs" structure contains two extra entries which are
+ /*
+ * Note that the "regs" structure contains two extra entries which are
* not really registers: a trap number which says what interrupt or
* trap made the switcher code come back, and an error code which some
- * traps set. */
+ * traps set.
+ */
/* Restore SYSENTER if it's supposed to be on. */
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
- /* If the Guest page faulted, then the cr2 register will tell us the
+ /*
+ * If the Guest page faulted, then the cr2 register will tell us the
* bad virtual address. We have to grab this now, because once we
* re-enable interrupts an interrupt could fault and thus overwrite
- * cr2, or we could even move off to a different CPU. */
+ * cr2, or we could even move off to a different CPU.
+ */
if (cpu->regs->trapnum == 14)
cpu->arch.last_pagefault = read_cr2();
- /* Similarly, if we took a trap because the Guest used the FPU,
+ /*
+ * Similarly, if we took a trap because the Guest used the FPU,
* we have to restore the FPU it expects to see.
* math_state_restore() may sleep and we may even move off to
* a different CPU. So all the critical stuff should be done
- * before this. */
+ * before this.
+ */
else if (cpu->regs->trapnum == 7)
math_state_restore();
}
-/*H:130 Now we've examined the hypercall code; our Guest can make requests.
+/*H:130
+ * Now we've examined the hypercall code; our Guest can make requests.
* Our Guest is usually so well behaved; it never tries to do things it isn't
* allowed to, and uses hypercalls instead. Unfortunately, Linux's paravirtual
* infrastructure isn't quite complete, because it doesn't contain replacements
*
* When the Guest uses one of these instructions, we get a trap (General
* Protection Fault) and come here. We see if it's one of those troublesome
- * instructions and skip over it. We return true if we did. */
+ * instructions and skip over it. We return true if we did.
+ */
static int emulate_insn(struct lg_cpu *cpu)
{
u8 insn;
unsigned int insnlen = 0, in = 0, shift = 0;
- /* The eip contains the *virtual* address of the Guest's instruction:
- * guest_pa just subtracts the Guest's page_offset. */
+ /*
+ * The eip contains the *virtual* address of the Guest's instruction:
+ * guest_pa just subtracts the Guest's page_offset.
+ */
unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
- /* This must be the Guest kernel trying to do something, not userspace!
+ /*
+ * This must be the Guest kernel trying to do something, not userspace!
* The bottom two bits of the CS segment register are the privilege
- * level. */
+ * level.
+ */
if ((cpu->regs->cs & 3) != GUEST_PL)
return 0;
/* Decoding x86 instructions is icky. */
insn = lgread(cpu, physaddr, u8);
- /* 0x66 is an "operand prefix". It means it's using the upper 16 bits
- of the eax register. */
+ /*
+ * 0x66 is an "operand prefix". It means it's using the upper 16 bits
+ * of the eax register.
+ */
if (insn == 0x66) {
shift = 16;
/* The instruction is 1 byte so far, read the next byte. */
insn = lgread(cpu, physaddr + insnlen, u8);
}
- /* We can ignore the lower bit for the moment and decode the 4 opcodes
- * we need to emulate. */
+ /*
+ * We can ignore the lower bit for the moment and decode the 4 opcodes
+ * we need to emulate.
+ */
switch (insn & 0xFE) {
case 0xE4: /* in <next byte>,%al */
insnlen += 2;
return 0;
}
- /* If it was an "IN" instruction, they expect the result to be read
+ /*
+ * If it was an "IN" instruction, they expect the result to be read
* into %eax, so we change %eax. We always return all-ones, which
- * traditionally means "there's nothing there". */
+ * traditionally means "there's nothing there".
+ */
if (in) {
/* Lower bit tells is whether it's a 16 or 32 bit access */
if (insn & 0x1)
return 1;
}
-/* Our hypercalls mechanism used to be based on direct software interrupts.
+/*
+ * Our hypercalls mechanism used to be based on direct software interrupts.
* After Anthony's "Refactor hypercall infrastructure" kvm patch, we decided to
* change over to using kvm hypercalls.
*
*/
static void rewrite_hypercall(struct lg_cpu *cpu)
{
- /* This are the opcodes we use to patch the Guest. The opcode for "int
+ /*
+ * This are the opcodes we use to patch the Guest. The opcode for "int
* $0x1f" is "0xcd 0x1f" but vmcall instruction is 3 bytes long, so we
- * complete the sequence with a NOP (0x90). */
+ * complete the sequence with a NOP (0x90).
+ */
u8 insn[3] = {0xcd, 0x1f, 0x90};
__lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn));
- /* The above write might have caused a copy of that page to be made
+ /*
+ * The above write might have caused a copy of that page to be made
* (if it was read-only). We need to make sure the Guest has
* up-to-date pagetables. As this doesn't happen often, we can just
- * drop them all. */
+ * drop them all.
+ */
guest_pagetable_clear_all(cpu);
}
{
u8 insn[3];
- /* This must be the Guest kernel trying to do something.
+ /*
+ * This must be the Guest kernel trying to do something.
* The bottom two bits of the CS segment register are the privilege
- * level. */
+ * level.
+ */
if ((cpu->regs->cs & 3) != GUEST_PL)
return false;
{
switch (cpu->regs->trapnum) {
case 13: /* We've intercepted a General Protection Fault. */
- /* Check if this was one of those annoying IN or OUT
+ /*
+ * Check if this was one of those annoying IN or OUT
* instructions which we need to emulate. If so, we just go
- * back into the Guest after we've done it. */
+ * back into the Guest after we've done it.
+ */
if (cpu->regs->errcode == 0) {
if (emulate_insn(cpu))
return;
}
- /* If KVM is active, the vmcall instruction triggers a
- * General Protection Fault. Normally it triggers an
- * invalid opcode fault (6): */
+ /*
+ * If KVM is active, the vmcall instruction triggers a General
+ * Protection Fault. Normally it triggers an invalid opcode
+ * fault (6):
+ */
case 6:
- /* We need to check if ring == GUEST_PL and
- * faulting instruction == vmcall. */
+ /*
+ * We need to check if ring == GUEST_PL and faulting
+ * instruction == vmcall.
+ */
if (is_hypercall(cpu)) {
rewrite_hypercall(cpu);
return;
}
break;
case 14: /* We've intercepted a Page Fault. */
- /* The Guest accessed a virtual address that wasn't mapped.
+ /*
+ * The Guest accessed a virtual address that wasn't mapped.
* This happens a lot: we don't actually set up most of the page
* tables for the Guest at all when we start: as it runs it asks
* for more and more, and we set them up as required. In this
* case, we don't even tell the Guest that the fault happened.
*
* The errcode tells whether this was a read or a write, and
- * whether kernel or userspace code. */
+ * whether kernel or userspace code.
+ */
if (demand_page(cpu, cpu->arch.last_pagefault,
cpu->regs->errcode))
return;
- /* OK, it's really not there (or not OK): the Guest needs to
+ /*
+ * OK, it's really not there (or not OK): the Guest needs to
* know. We write out the cr2 value so it knows where the
* fault occurred.
*
* Note that if the Guest were really messed up, this could
* happen before it's done the LHCALL_LGUEST_INIT hypercall, so
- * lg->lguest_data could be NULL */
+ * lg->lguest_data could be NULL
+ */
if (cpu->lg->lguest_data &&
put_user(cpu->arch.last_pagefault,
&cpu->lg->lguest_data->cr2))
kill_guest(cpu, "Writing cr2");
break;
case 7: /* We've intercepted a Device Not Available fault. */
- /* If the Guest doesn't want to know, we already restored the
- * Floating Point Unit, so we just continue without telling
- * it. */
+ /*
+ * If the Guest doesn't want to know, we already restored the
+ * Floating Point Unit, so we just continue without telling it.
+ */
if (!cpu->ts)
return;
break;
case 32 ... 255:
- /* These values mean a real interrupt occurred, in which case
+ /*
+ * These values mean a real interrupt occurred, in which case
* the Host handler has already been run. We just do a
* friendly check if another process should now be run, then
- * return to run the Guest again */
+ * return to run the Guest again
+ */
cond_resched();
return;
case LGUEST_TRAP_ENTRY:
- /* Our 'struct hcall_args' maps directly over our regs: we set
- * up the pointer now to indicate a hypercall is pending. */
+ /*
+ * Our 'struct hcall_args' maps directly over our regs: we set
+ * up the pointer now to indicate a hypercall is pending.
+ */
cpu->hcall = (struct hcall_args *)cpu->regs;
return;
}
/* We didn't handle the trap, so it needs to go to the Guest. */
if (!deliver_trap(cpu, cpu->regs->trapnum))
- /* If the Guest doesn't have a handler (either it hasn't
+ /*
+ * If the Guest doesn't have a handler (either it hasn't
* registered any yet, or it's one of the faults we don't let
- * it handle), it dies with this cryptic error message. */
+ * it handle), it dies with this cryptic error message.
+ */
kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)",
cpu->regs->trapnum, cpu->regs->eip,
cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault
: cpu->regs->errcode);
}
-/* Now we can look at each of the routines this calls, in increasing order of
+/*
+ * Now we can look at each of the routines this calls, in increasing order of
* complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(),
* deliver_trap() and demand_page(). After all those, we'll be ready to
* examine the Switcher, and our philosophical understanding of the Host/Guest
- * duality will be complete. :*/
+ * duality will be complete.
+:*/
static void adjust_pge(void *on)
{
if (on)
write_cr4(read_cr4() & ~X86_CR4_PGE);
}
-/*H:020 Now the Switcher is mapped and every thing else is ready, we need to do
- * some more i386-specific initialization. */
+/*H:020
+ * Now the Switcher is mapped and every thing else is ready, we need to do
+ * some more i386-specific initialization.
+ */
void __init lguest_arch_host_init(void)
{
int i;
- /* Most of the i386/switcher.S doesn't care that it's been moved; on
+ /*
+ * Most of the i386/switcher.S doesn't care that it's been moved; on
* Intel, jumps are relative, and it doesn't access any references to
* external code or data.
*
* addresses are placed in a table (default_idt_entries), so we need to
* update the table with the new addresses. switcher_offset() is a
* convenience function which returns the distance between the
- * compiled-in switcher code and the high-mapped copy we just made. */
+ * compiled-in switcher code and the high-mapped copy we just made.
+ */
for (i = 0; i < IDT_ENTRIES; i++)
default_idt_entries[i] += switcher_offset();
for_each_possible_cpu(i) {
/* lguest_pages() returns this CPU's two pages. */
struct lguest_pages *pages = lguest_pages(i);
- /* This is a convenience pointer to make the code fit one
- * statement to a line. */
+ /* This is a convenience pointer to make the code neater. */
struct lguest_ro_state *state = &pages->state;
- /* The Global Descriptor Table: the Host has a different one
+ /*
+ * The Global Descriptor Table: the Host has a different one
* for each CPU. We keep a descriptor for the GDT which says
* where it is and how big it is (the size is actually the last
- * byte, not the size, hence the "-1"). */
+ * byte, not the size, hence the "-1").
+ */
state->host_gdt_desc.size = GDT_SIZE-1;
state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
- /* All CPUs on the Host use the same Interrupt Descriptor
+ /*
+ * All CPUs on the Host use the same Interrupt Descriptor
* Table, so we just use store_idt(), which gets this CPU's IDT
- * descriptor. */
+ * descriptor.
+ */
store_idt(&state->host_idt_desc);
- /* The descriptors for the Guest's GDT and IDT can be filled
+ /*
+ * The descriptors for the Guest's GDT and IDT can be filled
* out now, too. We copy the GDT & IDT into ->guest_gdt and
- * ->guest_idt before actually running the Guest. */
+ * ->guest_idt before actually running the Guest.
+ */
state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
state->guest_idt_desc.address = (long)&state->guest_idt;
state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
state->guest_gdt_desc.address = (long)&state->guest_gdt;
- /* We know where we want the stack to be when the Guest enters
+ /*
+ * We know where we want the stack to be when the Guest enters
* the Switcher: in pages->regs. The stack grows upwards, so
- * we start it at the end of that structure. */
+ * we start it at the end of that structure.
+ */
state->guest_tss.sp0 = (long)(&pages->regs + 1);
- /* And this is the GDT entry to use for the stack: we keep a
- * couple of special LGUEST entries. */
+ /*
+ * And this is the GDT entry to use for the stack: we keep a
+ * couple of special LGUEST entries.
+ */
state->guest_tss.ss0 = LGUEST_DS;
- /* x86 can have a finegrained bitmap which indicates what I/O
+ /*
+ * x86 can have a finegrained bitmap which indicates what I/O
* ports the process can use. We set it to the end of our
- * structure, meaning "none". */
+ * structure, meaning "none".
+ */
state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
- /* Some GDT entries are the same across all Guests, so we can
- * set them up now. */
+ /*
+ * Some GDT entries are the same across all Guests, so we can
+ * set them up now.
+ */
setup_default_gdt_entries(state);
/* Most IDT entries are the same for all Guests, too.*/
setup_default_idt_entries(state, default_idt_entries);
- /* The Host needs to be able to use the LGUEST segments on this
- * CPU, too, so put them in the Host GDT. */
+ /*
+ * The Host needs to be able to use the LGUEST segments on this
+ * CPU, too, so put them in the Host GDT.
+ */
get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
}
- /* In the Switcher, we want the %cs segment register to use the
+ /*
+ * In the Switcher, we want the %cs segment register to use the
* LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
* it will be undisturbed when we switch. To change %cs and jump we
- * need this structure to feed to Intel's "lcall" instruction. */
+ * need this structure to feed to Intel's "lcall" instruction.
+ */
lguest_entry.offset = (long)switch_to_guest + switcher_offset();
lguest_entry.segment = LGUEST_CS;
- /* Finally, we need to turn off "Page Global Enable". PGE is an
+ /*
+ * Finally, we need to turn off "Page Global Enable". PGE is an
* optimization where page table entries are specially marked to show
* they never change. The Host kernel marks all the kernel pages this
* way because it's always present, even when userspace is running.
* you'll get really weird bugs that you'll chase for two days.
*
* I used to turn PGE off every time we switched to the Guest and back
- * on when we return, but that slowed the Switcher down noticibly. */
+ * on when we return, but that slowed the Switcher down noticibly.
+ */
- /* We don't need the complexity of CPUs coming and going while we're
- * doing this. */
+ /*
+ * We don't need the complexity of CPUs coming and going while we're
+ * doing this.
+ */
get_online_cpus();
if (cpu_has_pge) { /* We have a broader idea of "global". */
/* Remember that this was originally set (for cleanup). */
cpu_had_pge = 1;
- /* adjust_pge is a helper function which sets or unsets the PGE
- * bit on its CPU, depending on the argument (0 == unset). */
+ /*
+ * adjust_pge is a helper function which sets or unsets the PGE
+ * bit on its CPU, depending on the argument (0 == unset).
+ */
on_each_cpu(adjust_pge, (void *)0, 1);
/* Turn off the feature in the global feature set. */
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
{
u32 tsc_speed;
- /* The pointer to the Guest's "struct lguest_data" is the only argument.
- * We check that address now. */
+ /*
+ * The pointer to the Guest's "struct lguest_data" is the only argument.
+ * We check that address now.
+ */
if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1,
sizeof(*cpu->lg->lguest_data)))
return -EFAULT;
- /* Having checked it, we simply set lg->lguest_data to point straight
+ /*
+ * Having checked it, we simply set lg->lguest_data to point straight
* into the Launcher's memory at the right place and then use
* copy_to_user/from_user from now on, instead of lgread/write. I put
* this in to show that I'm not immune to writing stupid
- * optimizations. */
+ * optimizations.
+ */
cpu->lg->lguest_data = cpu->lg->mem_base + cpu->hcall->arg1;
- /* We insist that the Time Stamp Counter exist and doesn't change with
+ /*
+ * We insist that the Time Stamp Counter exist and doesn't change with
* cpu frequency. Some devious chip manufacturers decided that TSC
* changes could be handled in software. I decided that time going
* backwards might be good for benchmarks, but it's bad for users.
*
* We also insist that the TSC be stable: the kernel detects unreliable
- * TSCs for its own purposes, and we use that here. */
+ * TSCs for its own purposes, and we use that here.
+ */
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())
tsc_speed = tsc_khz;
else
}
/*:*/
-/*L:030 lguest_arch_setup_regs()
+/*L:030
+ * lguest_arch_setup_regs()
*
* Most of the Guest's registers are left alone: we used get_zeroed_page() to
- * allocate the structure, so they will be 0. */
+ * allocate the structure, so they will be 0.
+ */
void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start)
{
struct lguest_regs *regs = cpu->regs;
- /* There are four "segment" registers which the Guest needs to boot:
+ /*
+ * There are four "segment" registers which the Guest needs to boot:
* The "code segment" register (cs) refers to the kernel code segment
* __KERNEL_CS, and the "data", "extra" and "stack" segment registers
* refer to the kernel data segment __KERNEL_DS.
*
* The privilege level is packed into the lower bits. The Guest runs
- * at privilege level 1 (GUEST_PL).*/
+ * at privilege level 1 (GUEST_PL).
+ */
regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL;
regs->cs = __KERNEL_CS|GUEST_PL;
- /* The "eflags" register contains miscellaneous flags. Bit 1 (0x002)
+ /*
+ * The "eflags" register contains miscellaneous flags. Bit 1 (0x002)
* is supposed to always be "1". Bit 9 (0x200) controls whether
* interrupts are enabled. We always leave interrupts enabled while
- * running the Guest. */
+ * running the Guest.
+ */
regs->eflags = X86_EFLAGS_IF | 0x2;
- /* The "Extended Instruction Pointer" register says where the Guest is
- * running. */
+ /*
+ * The "Extended Instruction Pointer" register says where the Guest is
+ * running.
+ */
regs->eip = start;
- /* %esi points to our boot information, at physical address 0, so don't
- * touch it. */
+ /*
+ * %esi points to our boot information, at physical address 0, so don't
+ * touch it.
+ */
- /* There are a couple of GDT entries the Guest expects when first
- * booting. */
+ /* There are a couple of GDT entries the Guest expects at boot. */
setup_guest_gdt(cpu);
}
-/*P:900 This is the Switcher: code which sits at 0xFFC00000 astride both the
+/*P:900
+ * This is the Switcher: code which sits at 0xFFC00000 astride both the
* Host and Guest to do the low-level Guest<->Host switch. It is as simple as
* it can be made, but it's naturally very specific to x86.
*
* You have now completed Preparation. If this has whet your appetite; if you
* are feeling invigorated and refreshed then the next, more challenging stage
- * can be found in "make Guest". :*/
+ * can be found in "make Guest".
+ :*/
-/*M:012 Lguest is meant to be simple: my rule of thumb is that 1% more LOC must
+/*M:012
+ * Lguest is meant to be simple: my rule of thumb is that 1% more LOC must
* gain at least 1% more performance. Since neither LOC nor performance can be
* measured beforehand, it generally means implementing a feature then deciding
* if it's worth it. And once it's implemented, who can say no?
* Host (which is actually really easy).
*
* Two questions remain. Would the performance gain outweigh the complexity?
- * And who would write the verse documenting it? :*/
+ * And who would write the verse documenting it?
+:*/
-/*M:011 Lguest64 handles NMI. This gave me NMI envy (until I looked at their
+/*M:011
+ * Lguest64 handles NMI. This gave me NMI envy (until I looked at their
* code). It's worth doing though, since it would let us use oprofile in the
- * Host when a Guest is running. :*/
+ * Host when a Guest is running.
+:*/
/*S:100
* Welcome to the Switcher itself!
-/* Things the lguest guest needs to know. Note: like all lguest interfaces,
- * this is subject to wild and random change between versions. */
+/*
+ * Things the lguest guest needs to know. Note: like all lguest interfaces,
+ * this is subject to wild and random change between versions.
+ */
#ifndef _LINUX_LGUEST_H
#define _LINUX_LGUEST_H
#define LG_CLOCK_MIN_DELTA 100UL
#define LG_CLOCK_MAX_DELTA ULONG_MAX
-/*G:031 The second method of communicating with the Host is to via "struct
+/*G:031
+ * The second method of communicating with the Host is to via "struct
* lguest_data". Once the Guest's initialization hypercall tells the Host where
- * this is, the Guest and Host both publish information in it. :*/
+ * this is, the Guest and Host both publish information in it.
+:*/
struct lguest_data
{
- /* 512 == enabled (same as eflags in normal hardware). The Guest
- * changes interrupts so often that a hypercall is too slow. */
+ /*
+ * 512 == enabled (same as eflags in normal hardware). The Guest
+ * changes interrupts so often that a hypercall is too slow.
+ */
unsigned int irq_enabled;
/* Fine-grained interrupt disabling by the Guest */
DECLARE_BITMAP(blocked_interrupts, LGUEST_IRQS);
- /* The Host writes the virtual address of the last page fault here,
+ /*
+ * The Host writes the virtual address of the last page fault here,
* which saves the Guest a hypercall. CR2 is the native register where
- * this address would normally be found. */
+ * this address would normally be found.
+ */
unsigned long cr2;
/* Wallclock time set by the Host. */
struct timespec time;
- /* Interrupt pending set by the Host. The Guest should do a hypercall
- * if it re-enables interrupts and sees this set (to X86_EFLAGS_IF). */
+ /*
+ * Interrupt pending set by the Host. The Guest should do a hypercall
+ * if it re-enables interrupts and sees this set (to X86_EFLAGS_IF).
+ */
int irq_pending;
- /* Async hypercall ring. Instead of directly making hypercalls, we can
+ /*
+ * Async hypercall ring. Instead of directly making hypercalls, we can
* place them in here for processing the next time the Host wants.
- * This batching can be quite efficient. */
+ * This batching can be quite efficient.
+ */
/* 0xFF == done (set by Host), 0 == pending (set by Guest). */
u8 hcall_status[LHCALL_RING_SIZE];
__u8 type;
/* The number of virtqueues (first in config array) */
__u8 num_vq;
- /* The number of bytes of feature bits. Multiply by 2: one for host
- * features and one for Guest acknowledgements. */
+ /*
+ * The number of bytes of feature bits. Multiply by 2: one for host
+ * features and one for Guest acknowledgements.
+ */
__u8 feature_len;
/* The number of bytes of the config array after virtqueues. */
__u8 config_len;
__u8 config[0];
};
-/*D:135 This is how we expect the device configuration field for a virtqueue
- * to be laid out in config space. */
+/*D:135
+ * This is how we expect the device configuration field for a virtqueue
+ * to be laid out in config space.
+ */
struct lguest_vqconfig {
/* The number of entries in the virtio_ring */
__u16 num;
LHREQ_EVENTFD, /* + address, fd. */
};
-/* The alignment to use between consumer and producer parts of vring.
- * x86 pagesize for historical reasons. */
+/*
+ * The alignment to use between consumer and producer parts of vring.
+ * x86 pagesize for historical reasons.
+ */
#define LGUEST_VRING_ALIGN 4096
#endif /* _LINUX_LGUEST_LAUNCHER */
projects / linux-2.6-block.git / commitdiff