arch/x86/xen/enlighten.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
   4 #include <linux/memblock.h>
   5 #endif
   6 #include <linux/cpu.h>
   7 #include <linux/kexec.h>
   8 #include <linux/slab.h>
   9
  10 #include <xen/xen.h>
  11 #include <xen/features.h>
  12 #include <xen/page.h>
  13
  14 #include <asm/xen/hypercall.h>
  15 #include <asm/xen/hypervisor.h>
  16 #include <asm/cpu.h>
  17 #include <asm/e820/api.h>
  18
  19 #include "xen-ops.h"
  20 #include "smp.h"
  21 #include "pmu.h"
  22
  23 EXPORT_SYMBOL_GPL(hypercall_page);
  24
  25 /*
  26  * Pointer to the xen_vcpu_info structure or
  27  * &HYPERVISOR_shared_info->vcpu_info[cpu]. See xen_hvm_init_shared_info
  28  * and xen_vcpu_setup for details. By default it points to share_info->vcpu_info
  29  * but if the hypervisor supports VCPUOP_register_vcpu_info then it can point
  30  * to xen_vcpu_info. The pointer is used in __xen_evtchn_do_upcall to
  31  * acknowledge pending events.
  32  * Also more subtly it is used by the patched version of irq enable/disable
  33  * e.g. xen_irq_enable_direct and xen_iret in PV mode.
  34  *
  35  * The desire to be able to do those mask/unmask operations as a single
  36  * instruction by using the per-cpu offset held in %gs is the real reason
  37  * vcpu info is in a per-cpu pointer and the original reason for this
  38  * hypercall.
  39  *
  40  */
  41 DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
  42
  43 /*
  44  * Per CPU pages used if hypervisor supports VCPUOP_register_vcpu_info
  45  * hypercall. This can be used both in PV and PVHVM mode. The structure
  46  * overrides the default per_cpu(xen_vcpu, cpu) value.
  47  */
  48 DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);
  49
  50 /* Linux <-> Xen vCPU id mapping */
  51 DEFINE_PER_CPU(uint32_t, xen_vcpu_id);
  52 EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
  53
  54 enum xen_domain_type xen_domain_type = XEN_NATIVE;
  55 EXPORT_SYMBOL_GPL(xen_domain_type);
  56
  57 unsigned long *machine_to_phys_mapping = (void *)MACH2PHYS_VIRT_START;
  58 EXPORT_SYMBOL(machine_to_phys_mapping);
  59 unsigned long  machine_to_phys_nr;
  60 EXPORT_SYMBOL(machine_to_phys_nr);
  61
  62 struct start_info *xen_start_info;
  63 EXPORT_SYMBOL_GPL(xen_start_info);
  64
  65 struct shared_info xen_dummy_shared_info;
  66
  67 __read_mostly int xen_have_vector_callback;
  68 EXPORT_SYMBOL_GPL(xen_have_vector_callback);
  69
  70 /*
  71  * NB: needs to live in .data because it's used by xen_prepare_pvh which runs
  72  * before clearing the bss.
  73  */
  74 uint32_t xen_start_flags __attribute__((section(".data"))) = 0;
  75 EXPORT_SYMBOL(xen_start_flags);
  76
  77 /*
  78  * Point at some empty memory to start with. We map the real shared_info
  79  * page as soon as fixmap is up and running.
  80  */
  81 struct shared_info *HYPERVISOR_shared_info = &xen_dummy_shared_info;
  82
  83 /*
  84  * Flag to determine whether vcpu info placement is available on all
  85  * VCPUs.  We assume it is to start with, and then set it to zero on
  86  * the first failure.  This is because it can succeed on some VCPUs
  87  * and not others, since it can involve hypervisor memory allocation,
  88  * or because the guest failed to guarantee all the appropriate
  89  * constraints on all VCPUs (ie buffer can't cross a page boundary).
  90  *
  91  * Note that any particular CPU may be using a placed vcpu structure,
  92  * but we can only optimise if the all are.
  93  *
  94  * 0: not available, 1: available
  95  */
  96 int xen_have_vcpu_info_placement = 1;
  97
  98 static int xen_cpu_up_online(unsigned int cpu)
  99 {
 100         xen_init_lock_cpu(cpu);
 101         return 0;
 102 }
 103
 104 int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned int),
 105                     int (*cpu_dead_cb)(unsigned int))
 106 {
 107         int rc;
 108
 109         rc = cpuhp_setup_state_nocalls(CPUHP_XEN_PREPARE,
 110                                        "x86/xen/guest:prepare",
 111                                        cpu_up_prepare_cb, cpu_dead_cb);
 112         if (rc >= 0) {
 113                 rc = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
 114                                                "x86/xen/guest:online",
 115                                                xen_cpu_up_online, NULL);
 116                 if (rc < 0)
 117                         cpuhp_remove_state_nocalls(CPUHP_XEN_PREPARE);
 118         }
 119
 120         return rc >= 0 ? 0 : rc;
 121 }
 122
 123 static int xen_vcpu_setup_restore(int cpu)
 124 {
 125         int rc = 0;
 126
 127         /* Any per_cpu(xen_vcpu) is stale, so reset it */
 128         xen_vcpu_info_reset(cpu);
 129
 130         /*
 131          * For PVH and PVHVM, setup online VCPUs only. The rest will
 132          * be handled by hotplug.
 133          */
 134         if (xen_pv_domain() ||
 135             (xen_hvm_domain() && cpu_online(cpu))) {
 136                 rc = xen_vcpu_setup(cpu);
 137         }
 138
 139         return rc;
 140 }
 141
 142 /*
 143  * On restore, set the vcpu placement up again.
 144  * If it fails, then we're in a bad state, since
 145  * we can't back out from using it...
 146  */
 147 void xen_vcpu_restore(void)
 148 {
 149         int cpu, rc;
 150
 151         for_each_possible_cpu(cpu) {
 152                 bool other_cpu = (cpu != smp_processor_id());
 153                 bool is_up;
 154
 155                 if (xen_vcpu_nr(cpu) == XEN_VCPU_ID_INVALID)
 156                         continue;
 157
 158                 /* Only Xen 4.5 and higher support this. */
 159                 is_up = HYPERVISOR_vcpu_op(VCPUOP_is_up,
 160                                            xen_vcpu_nr(cpu), NULL) > 0;
 161
 162                 if (other_cpu && is_up &&
 163                     HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL))
 164                         BUG();
 165
 166                 if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock))
 167                         xen_setup_runstate_info(cpu);
 168
 169                 rc = xen_vcpu_setup_restore(cpu);
 170                 if (rc)
 171                         pr_emerg_once("vcpu restore failed for cpu=%d err=%d. "
 172                                         "System will hang.\n", cpu, rc);
 173                 /*
 174                  * In case xen_vcpu_setup_restore() fails, do not bring up the
 175                  * VCPU. This helps us avoid the resulting OOPS when the VCPU
 176                  * accesses pvclock_vcpu_time via xen_vcpu (which is NULL.)
 177                  * Note that this does not improve the situation much -- now the
 178                  * VM hangs instead of OOPSing -- with the VCPUs that did not
 179                  * fail, spinning in stop_machine(), waiting for the failed
 180                  * VCPUs to come up.
 181                  */
 182                 if (other_cpu && is_up && (rc == 0) &&
 183                     HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL))
 184                         BUG();
 185         }
 186 }
 187
 188 void xen_vcpu_info_reset(int cpu)
 189 {
 190         if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS) {
 191                 per_cpu(xen_vcpu, cpu) =
 192                         &HYPERVISOR_shared_info->vcpu_info[xen_vcpu_nr(cpu)];
 193         } else {
 194                 /* Set to NULL so that if somebody accesses it we get an OOPS */
 195                 per_cpu(xen_vcpu, cpu) = NULL;
 196         }
 197 }
 198
 199 int xen_vcpu_setup(int cpu)
 200 {
 201         struct vcpu_register_vcpu_info info;
 202         int err;
 203         struct vcpu_info *vcpup;
 204
 205         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 206
 207         /*
 208          * This path is called on PVHVM at bootup (xen_hvm_smp_prepare_boot_cpu)
 209          * and at restore (xen_vcpu_restore). Also called for hotplugged
 210          * VCPUs (cpu_init -> xen_hvm_cpu_prepare_hvm).
 211          * However, the hypercall can only be done once (see below) so if a VCPU
 212          * is offlined and comes back online then let's not redo the hypercall.
 213          *
 214          * For PV it is called during restore (xen_vcpu_restore) and bootup
 215          * (xen_setup_vcpu_info_placement). The hotplug mechanism does not
 216          * use this function.
 217          */
 218         if (xen_hvm_domain()) {
 219                 if (per_cpu(xen_vcpu, cpu) == &per_cpu(xen_vcpu_info, cpu))
 220                         return 0;
 221         }
 222
 223         if (xen_have_vcpu_info_placement) {
 224                 vcpup = &per_cpu(xen_vcpu_info, cpu);
 225                 info.mfn = arbitrary_virt_to_mfn(vcpup);
 226                 info.offset = offset_in_page(vcpup);
 227
 228                 /*
 229                  * Check to see if the hypervisor will put the vcpu_info
 230                  * structure where we want it, which allows direct access via
 231                  * a percpu-variable.
 232                  * N.B. This hypercall can _only_ be called once per CPU.
 233                  * Subsequent calls will error out with -EINVAL. This is due to
 234                  * the fact that hypervisor has no unregister variant and this
 235                  * hypercall does not allow to over-write info.mfn and
 236                  * info.offset.
 237                  */
 238                 err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info,
 239                                          xen_vcpu_nr(cpu), &info);
 240
 241                 if (err) {
 242                         pr_warn_once("register_vcpu_info failed: cpu=%d err=%d\n",
 243                                      cpu, err);
 244                         xen_have_vcpu_info_placement = 0;
 245                 } else {
 246                         /*
 247                          * This cpu is using the registered vcpu info, even if
 248                          * later ones fail to.
 249                          */
 250                         per_cpu(xen_vcpu, cpu) = vcpup;
 251                 }
 252         }
 253
 254         if (!xen_have_vcpu_info_placement)
 255                 xen_vcpu_info_reset(cpu);
 256
 257         return ((per_cpu(xen_vcpu, cpu) == NULL) ? -ENODEV : 0);
 258 }
 259
 260 void xen_reboot(int reason)
 261 {
 262         struct sched_shutdown r = { .reason = reason };
 263         int cpu;
 264
 265         for_each_online_cpu(cpu)
 266                 xen_pmu_finish(cpu);
 267
 268         if (HYPERVISOR_sched_op(SCHEDOP_shutdown, &r))
 269                 BUG();
 270 }
 271
 272 void xen_emergency_restart(void)
 273 {
 274         xen_reboot(SHUTDOWN_reboot);
 275 }
 276
 277 static int
 278 xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
 279 {
 280         if (!kexec_crash_loaded())
 281                 xen_reboot(SHUTDOWN_crash);
 282         return NOTIFY_DONE;
 283 }
 284
 285 static struct notifier_block xen_panic_block = {
 286         .notifier_call = xen_panic_event,
 287         .priority = INT_MIN
 288 };
 289
 290 int xen_panic_handler_init(void)
 291 {
 292         atomic_notifier_chain_register(&panic_notifier_list, &xen_panic_block);
 293         return 0;
 294 }
 295
 296 void xen_pin_vcpu(int cpu)
 297 {
 298         static bool disable_pinning;
 299         struct sched_pin_override pin_override;
 300         int ret;
 301
 302         if (disable_pinning)
 303                 return;
 304
 305         pin_override.pcpu = cpu;
 306         ret = HYPERVISOR_sched_op(SCHEDOP_pin_override, &pin_override);
 307
 308         /* Ignore errors when removing override. */
 309         if (cpu < 0)
 310                 return;
 311
 312         switch (ret) {
 313         case -ENOSYS:
 314                 pr_warn("Unable to pin on physical cpu %d. In case of problems consider vcpu pinning.\n",
 315                         cpu);
 316                 disable_pinning = true;
 317                 break;
 318         case -EPERM:
 319                 WARN(1, "Trying to pin vcpu without having privilege to do so\n");
 320                 disable_pinning = true;
 321                 break;
 322         case -EINVAL:
 323         case -EBUSY:
 324                 pr_warn("Physical cpu %d not available for pinning. Check Xen cpu configuration.\n",
 325                         cpu);
 326                 break;
 327         case 0:
 328                 break;
 329         default:
 330                 WARN(1, "rc %d while trying to pin vcpu\n", ret);
 331                 disable_pinning = true;
 332         }
 333 }
 334
 335 #ifdef CONFIG_HOTPLUG_CPU
 336 void xen_arch_register_cpu(int num)
 337 {
 338         arch_register_cpu(num);
 339 }
 340 EXPORT_SYMBOL(xen_arch_register_cpu);
 341
 342 void xen_arch_unregister_cpu(int num)
 343 {
 344         arch_unregister_cpu(num);
 345 }
 346 EXPORT_SYMBOL(xen_arch_unregister_cpu);
 347 #endif