arch/x86/xen/smp_pv.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Xen SMP support
   4  *
   5  * This file implements the Xen versions of smp_ops.  SMP under Xen is
   6  * very straightforward.  Bringing a CPU up is simply a matter of
   7  * loading its initial context and setting it running.
   8  *
   9  * IPIs are handled through the Xen event mechanism.
  10  *
  11  * Because virtual CPUs can be scheduled onto any real CPU, there's no
  12  * useful topology information for the kernel to make use of.  As a
  13  * result, all CPUs are treated as if they're single-core and
  14  * single-threaded.
  15  */
  16 #include <linux/sched.h>
  17 #include <linux/sched/task_stack.h>
  18 #include <linux/err.h>
  19 #include <linux/slab.h>
  20 #include <linux/smp.h>
  21 #include <linux/irq_work.h>
  22 #include <linux/tick.h>
  23 #include <linux/nmi.h>
  24 #include <linux/cpuhotplug.h>
  25 #include <linux/stackprotector.h>
  26 #include <linux/pgtable.h>
  27
  28 #include <asm/paravirt.h>
  29 #include <asm/idtentry.h>
  30 #include <asm/desc.h>
  31 #include <asm/cpu.h>
  32 #include <asm/apic.h>
  33 #include <asm/io_apic.h>
  34
  35 #include <xen/interface/xen.h>
  36 #include <xen/interface/vcpu.h>
  37 #include <xen/interface/xenpmu.h>
  38
  39 #include <asm/spec-ctrl.h>
  40 #include <asm/xen/interface.h>
  41 #include <asm/xen/hypercall.h>
  42
  43 #include <xen/xen.h>
  44 #include <xen/page.h>
  45 #include <xen/events.h>
  46
  47 #include <xen/hvc-console.h>
  48 #include "xen-ops.h"
  49 #include "mmu.h"
  50 #include "smp.h"
  51 #include "pmu.h"
  52
  53 cpumask_var_t xen_cpu_initialized_map;
  54
  55 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  56 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  57
  58 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  59
  60 static void cpu_bringup(void)
  61 {
  62         int cpu;
  63
  64         cr4_init();
  65         cpuhp_ap_sync_alive();
  66         cpu_init();
  67         fpu__init_cpu();
  68         touch_softlockup_watchdog();
  69
  70         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  71         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  72                 xen_enable_sysenter();
  73                 xen_enable_syscall();
  74         }
  75         cpu = smp_processor_id();
  76         smp_store_cpu_info(cpu);
  77         set_cpu_sibling_map(cpu);
  78
  79         speculative_store_bypass_ht_init();
  80
  81         xen_setup_cpu_clockevents();
  82
  83         notify_cpu_starting(cpu);
  84
  85         set_cpu_online(cpu, true);
  86
  87         smp_mb();
  88
  89         /* We can take interrupts now: we're officially "up". */
  90         local_irq_enable();
  91 }
  92
  93 asmlinkage __visible void cpu_bringup_and_idle(void)
  94 {
  95         cpu_bringup();
  96         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  97 }
  98
  99 void xen_smp_intr_free_pv(unsigned int cpu)
 100 {
 101         kfree(per_cpu(xen_irq_work, cpu).name);
 102         per_cpu(xen_irq_work, cpu).name = NULL;
 103         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
 104                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 105                 per_cpu(xen_irq_work, cpu).irq = -1;
 106         }
 107
 108         kfree(per_cpu(xen_pmu_irq, cpu).name);
 109         per_cpu(xen_pmu_irq, cpu).name = NULL;
 110         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 111                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 112                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 113         }
 114 }
 115
 116 int xen_smp_intr_init_pv(unsigned int cpu)
 117 {
 118         int rc;
 119         char *callfunc_name, *pmu_name;
 120
 121         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 122         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 123         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 124                                     cpu,
 125                                     xen_irq_work_interrupt,
 126                                     IRQF_PERCPU|IRQF_NOBALANCING,
 127                                     callfunc_name,
 128                                     NULL);
 129         if (rc < 0)
 130                 goto fail;
 131         per_cpu(xen_irq_work, cpu).irq = rc;
 132
 133         if (is_xen_pmu) {
 134                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 135                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 136                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 137                                              xen_pmu_irq_handler,
 138                                              IRQF_PERCPU|IRQF_NOBALANCING,
 139                                              pmu_name, NULL);
 140                 if (rc < 0)
 141                         goto fail;
 142                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 143         }
 144
 145         return 0;
 146
 147  fail:
 148         xen_smp_intr_free_pv(cpu);
 149         return rc;
 150 }
 151
 152 static void __init xen_pv_smp_config(void)
 153 {
 154         u32 apicid = 0;
 155         int i;
 156
 157         topology_register_boot_apic(apicid++);
 158
 159         for (i = 1; i < nr_cpu_ids; i++)
 160                 topology_register_apic(apicid++, CPU_ACPIID_INVALID, true);
 161
 162         /* Pretend to be a proper enumerated system */
 163         smp_found_config = 1;
 164 }
 165
 166 static void __init xen_pv_smp_prepare_boot_cpu(void)
 167 {
 168         BUG_ON(smp_processor_id() != 0);
 169         native_smp_prepare_boot_cpu();
 170
 171         if (!xen_feature(XENFEAT_writable_page_tables))
 172                 /* We've switched to the "real" per-cpu gdt, so make
 173                  * sure the old memory can be recycled. */
 174                 make_lowmem_page_readwrite(xen_initial_gdt);
 175
 176         xen_setup_vcpu_info_placement();
 177
 178         /*
 179          * The alternative logic (which patches the unlock/lock) runs before
 180          * the smp bootup up code is activated. Hence we need to set this up
 181          * the core kernel is being patched. Otherwise we will have only
 182          * modules patched but not core code.
 183          */
 184         xen_init_spinlocks();
 185 }
 186
 187 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 188 {
 189         unsigned cpu;
 190
 191         if (ioapic_is_disabled) {
 192                 char *m = (max_cpus == 0) ?
 193                         "The nosmp parameter is incompatible with Xen; " \
 194                         "use Xen dom0_max_vcpus=1 parameter" :
 195                         "The noapic parameter is incompatible with Xen";
 196
 197                 xen_raw_printk(m);
 198                 panic(m);
 199         }
 200         xen_init_lock_cpu(0);
 201
 202         smp_prepare_cpus_common();
 203
 204         speculative_store_bypass_ht_init();
 205
 206         xen_pmu_init(0);
 207
 208         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 209                 BUG();
 210
 211         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 212                 panic("could not allocate xen_cpu_initialized_map\n");
 213
 214         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 215
 216         /* Restrict the possible_map according to max_cpus. */
 217         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 218                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 219                         continue;
 220                 set_cpu_possible(cpu, false);
 221         }
 222
 223         for_each_possible_cpu(cpu)
 224                 set_cpu_present(cpu, true);
 225 }
 226
 227 static int
 228 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 229 {
 230         struct vcpu_guest_context *ctxt;
 231         struct desc_struct *gdt;
 232         unsigned long gdt_mfn;
 233
 234         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 235                 return 0;
 236
 237         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 238         if (ctxt == NULL) {
 239                 cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
 240                 return -ENOMEM;
 241         }
 242
 243         gdt = get_cpu_gdt_rw(cpu);
 244
 245         /*
 246          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 247          * pointing just below where pt_regs would be if it were a normal
 248          * kernel entry.
 249          */
 250         ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
 251         ctxt->flags = VGCF_IN_KERNEL;
 252         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 253         ctxt->user_regs.ds = __USER_DS;
 254         ctxt->user_regs.es = __USER_DS;
 255         ctxt->user_regs.ss = __KERNEL_DS;
 256         ctxt->user_regs.cs = __KERNEL_CS;
 257         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 258
 259         xen_copy_trap_info(ctxt->trap_ctxt);
 260
 261         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 262
 263         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 264         make_lowmem_page_readonly(gdt);
 265         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 266
 267         ctxt->gdt_frames[0] = gdt_mfn;
 268         ctxt->gdt_ents      = GDT_ENTRIES;
 269
 270         /*
 271          * Set SS:SP that Xen will use when entering guest kernel mode
 272          * from guest user mode.  Subsequent calls to load_sp0() can
 273          * change this value.
 274          */
 275         ctxt->kernel_ss = __KERNEL_DS;
 276         ctxt->kernel_sp = task_top_of_stack(idle);
 277
 278         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 279         ctxt->event_callback_eip    =
 280                 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
 281         ctxt->failsafe_callback_eip =
 282                 (unsigned long)xen_failsafe_callback;
 283         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 284
 285         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 286         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 287                 BUG();
 288
 289         kfree(ctxt);
 290         return 0;
 291 }
 292
 293 static int xen_pv_kick_ap(unsigned int cpu, struct task_struct *idle)
 294 {
 295         int rc;
 296
 297         rc = common_cpu_up(cpu, idle);
 298         if (rc)
 299                 return rc;
 300
 301         xen_setup_runstate_info(cpu);
 302
 303         /* make sure interrupts start blocked */
 304         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 305
 306         rc = cpu_initialize_context(cpu, idle);
 307         if (rc)
 308                 return rc;
 309
 310         xen_pmu_init(cpu);
 311
 312         /*
 313          * Why is this a BUG? If the hypercall fails then everything can be
 314          * rolled back, no?
 315          */
 316         BUG_ON(HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL));
 317
 318         return 0;
 319 }
 320
 321 static void xen_pv_poll_sync_state(void)
 322 {
 323         HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 324 }
 325
 326 #ifdef CONFIG_HOTPLUG_CPU
 327 static int xen_pv_cpu_disable(void)
 328 {
 329         unsigned int cpu = smp_processor_id();
 330         if (cpu == 0)
 331                 return -EBUSY;
 332
 333         cpu_disable_common();
 334
 335         load_cr3(swapper_pg_dir);
 336         return 0;
 337 }
 338
 339 static void xen_pv_cpu_die(unsigned int cpu)
 340 {
 341         while (HYPERVISOR_vcpu_op(VCPUOP_is_up, xen_vcpu_nr(cpu), NULL)) {
 342                 __set_current_state(TASK_UNINTERRUPTIBLE);
 343                 schedule_timeout(HZ/10);
 344         }
 345 }
 346
 347 static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
 348 {
 349         xen_smp_intr_free(cpu);
 350         xen_uninit_lock_cpu(cpu);
 351         xen_teardown_timer(cpu);
 352         xen_pmu_finish(cpu);
 353 }
 354
 355 static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 356 {
 357         play_dead_common();
 358         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 359         xen_cpu_bringup_again((unsigned long)task_pt_regs(current));
 360         BUG();
 361 }
 362
 363 #else /* !CONFIG_HOTPLUG_CPU */
 364 static int xen_pv_cpu_disable(void)
 365 {
 366         return -ENOSYS;
 367 }
 368
 369 static void xen_pv_cpu_die(unsigned int cpu)
 370 {
 371         BUG();
 372 }
 373
 374 static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
 375 {
 376         BUG();
 377 }
 378
 379 static void __noreturn xen_pv_play_dead(void)
 380 {
 381         BUG();
 382 }
 383
 384 #endif
 385 static void stop_self(void *v)
 386 {
 387         int cpu = smp_processor_id();
 388
 389         /* make sure we're not pinning something down */
 390         load_cr3(swapper_pg_dir);
 391         /* should set up a minimal gdt */
 392
 393         set_cpu_online(cpu, false);
 394
 395         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 396         BUG();
 397 }
 398
 399 static void xen_pv_stop_other_cpus(int wait)
 400 {
 401         smp_call_function(stop_self, NULL, wait);
 402 }
 403
 404 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 405 {
 406         irq_work_run();
 407         inc_irq_stat(apic_irq_work_irqs);
 408
 409         return IRQ_HANDLED;
 410 }
 411
 412 void __init xen_smp_count_cpus(void)
 413 {
 414         unsigned int cpus;
 415
 416         for (cpus = 0; cpus < nr_cpu_ids; cpus++) {
 417                 if (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpus, NULL) < 0)
 418                         break;
 419         }
 420
 421         pr_info("Xen PV: Detected %u vCPUS\n", cpus);
 422         if (cpus < nr_cpu_ids)
 423                 set_nr_cpu_ids(cpus);
 424 }
 425
 426 static const struct smp_ops xen_smp_ops __initconst = {
 427         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 428         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 429         .smp_cpus_done = xen_smp_cpus_done,
 430
 431         .kick_ap_alive = xen_pv_kick_ap,
 432         .cpu_die = xen_pv_cpu_die,
 433         .cleanup_dead_cpu = xen_pv_cleanup_dead_cpu,
 434         .poll_sync_state = xen_pv_poll_sync_state,
 435         .cpu_disable = xen_pv_cpu_disable,
 436         .play_dead = xen_pv_play_dead,
 437
 438         .stop_other_cpus = xen_pv_stop_other_cpus,
 439         .smp_send_reschedule = xen_smp_send_reschedule,
 440
 441         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 442         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 443 };
 444
 445 void __init xen_smp_init(void)
 446 {
 447         smp_ops = xen_smp_ops;
 448
 449         /* Avoid searching for BIOS MP tables */
 450         x86_init.mpparse.find_mptable           = x86_init_noop;
 451         x86_init.mpparse.early_parse_smp_cfg    = x86_init_noop;
 452
 453         /* XEN/PV Dom0 has halfways sane topology information via CPUID/MADT */
 454         if (xen_initial_domain())
 455                 x86_init.mpparse.parse_smp_cfg  = x86_init_noop;
 456         else
 457                 x86_init.mpparse.parse_smp_cfg  = xen_pv_smp_config;
 458 }