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