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/io_apic.h>
  33
  34 #include <xen/interface/xen.h>
  35 #include <xen/interface/vcpu.h>
  36 #include <xen/interface/xenpmu.h>
  37
  38 #include <asm/spec-ctrl.h>
  39 #include <asm/xen/interface.h>
  40 #include <asm/xen/hypercall.h>
  41
  42 #include <xen/xen.h>
  43 #include <xen/page.h>
  44 #include <xen/events.h>
  45
  46 #include <xen/hvc-console.h>
  47 #include "xen-ops.h"
  48 #include "mmu.h"
  49 #include "smp.h"
  50 #include "pmu.h"
  51
  52 cpumask_var_t xen_cpu_initialized_map;
  53
  54 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  55 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  56
  57 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  58 void asm_cpu_bringup_and_idle(void);
  59
  60 static void cpu_bringup(void)
  61 {
  62         int cpu;
  63
  64         cr4_init();
  65         cpu_init();
  66         touch_softlockup_watchdog();
  67         preempt_disable();
  68
  69         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  70         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  71                 xen_enable_sysenter();
  72                 xen_enable_syscall();
  73         }
  74         cpu = smp_processor_id();
  75         smp_store_cpu_info(cpu);
  76         cpu_data(cpu).x86_max_cores = 1;
  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         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  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         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
 102                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 103                 per_cpu(xen_irq_work, cpu).irq = -1;
 104                 kfree(per_cpu(xen_irq_work, cpu).name);
 105                 per_cpu(xen_irq_work, cpu).name = NULL;
 106         }
 107
 108         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 109                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 110                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 111                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 112                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 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         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 123                                     cpu,
 124                                     xen_irq_work_interrupt,
 125                                     IRQF_PERCPU|IRQF_NOBALANCING,
 126                                     callfunc_name,
 127                                     NULL);
 128         if (rc < 0)
 129                 goto fail;
 130         per_cpu(xen_irq_work, cpu).irq = rc;
 131         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 132
 133         if (is_xen_pmu(cpu)) {
 134                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 135                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 136                                              xen_pmu_irq_handler,
 137                                              IRQF_PERCPU|IRQF_NOBALANCING,
 138                                              pmu_name, NULL);
 139                 if (rc < 0)
 140                         goto fail;
 141                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 142                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 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_fill_possible_map(void)
 153 {
 154         int i, rc;
 155
 156         if (xen_initial_domain())
 157                 return;
 158
 159         for (i = 0; i < nr_cpu_ids; i++) {
 160                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 161                 if (rc >= 0) {
 162                         num_processors++;
 163                         set_cpu_possible(i, true);
 164                 }
 165         }
 166 }
 167
 168 static void __init xen_filter_cpu_maps(void)
 169 {
 170         int i, rc;
 171         unsigned int subtract = 0;
 172
 173         if (!xen_initial_domain())
 174                 return;
 175
 176         num_processors = 0;
 177         disabled_cpus = 0;
 178         for (i = 0; i < nr_cpu_ids; i++) {
 179                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 180                 if (rc >= 0) {
 181                         num_processors++;
 182                         set_cpu_possible(i, true);
 183                 } else {
 184                         set_cpu_possible(i, false);
 185                         set_cpu_present(i, false);
 186                         subtract++;
 187                 }
 188         }
 189 #ifdef CONFIG_HOTPLUG_CPU
 190         /* This is akin to using 'nr_cpus' on the Linux command line.
 191          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 192          * have up to X, while nr_cpu_ids is greater than X. This
 193          * normally is not a problem, except when CPU hotplugging
 194          * is involved and then there might be more than X CPUs
 195          * in the guest - which will not work as there is no
 196          * hypercall to expand the max number of VCPUs an already
 197          * running guest has. So cap it up to X. */
 198         if (subtract)
 199                 nr_cpu_ids = nr_cpu_ids - subtract;
 200 #endif
 201
 202 }
 203
 204 static void __init xen_pv_smp_prepare_boot_cpu(void)
 205 {
 206         BUG_ON(smp_processor_id() != 0);
 207         native_smp_prepare_boot_cpu();
 208
 209         if (!xen_feature(XENFEAT_writable_page_tables))
 210                 /* We've switched to the "real" per-cpu gdt, so make
 211                  * sure the old memory can be recycled. */
 212                 make_lowmem_page_readwrite(xen_initial_gdt);
 213
 214 #ifdef CONFIG_X86_32
 215         /*
 216          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 217          * expects __USER_DS
 218          */
 219         loadsegment(ds, __USER_DS);
 220         loadsegment(es, __USER_DS);
 221 #endif
 222
 223         xen_filter_cpu_maps();
 224         xen_setup_vcpu_info_placement();
 225
 226         /*
 227          * The alternative logic (which patches the unlock/lock) runs before
 228          * the smp bootup up code is activated. Hence we need to set this up
 229          * the core kernel is being patched. Otherwise we will have only
 230          * modules patched but not core code.
 231          */
 232         xen_init_spinlocks();
 233 }
 234
 235 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 236 {
 237         unsigned cpu;
 238         unsigned int i;
 239
 240         if (skip_ioapic_setup) {
 241                 char *m = (max_cpus == 0) ?
 242                         "The nosmp parameter is incompatible with Xen; " \
 243                         "use Xen dom0_max_vcpus=1 parameter" :
 244                         "The noapic parameter is incompatible with Xen";
 245
 246                 xen_raw_printk(m);
 247                 panic(m);
 248         }
 249         xen_init_lock_cpu(0);
 250
 251         smp_store_boot_cpu_info();
 252         cpu_data(0).x86_max_cores = 1;
 253
 254         for_each_possible_cpu(i) {
 255                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 256                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 257                 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
 258                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 259         }
 260         set_cpu_sibling_map(0);
 261
 262         speculative_store_bypass_ht_init();
 263
 264         xen_pmu_init(0);
 265
 266         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 267                 BUG();
 268
 269         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 270                 panic("could not allocate xen_cpu_initialized_map\n");
 271
 272         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 273
 274         /* Restrict the possible_map according to max_cpus. */
 275         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 276                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 277                         continue;
 278                 set_cpu_possible(cpu, false);
 279         }
 280
 281         for_each_possible_cpu(cpu)
 282                 set_cpu_present(cpu, true);
 283 }
 284
 285 static int
 286 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 287 {
 288         struct vcpu_guest_context *ctxt;
 289         struct desc_struct *gdt;
 290         unsigned long gdt_mfn;
 291
 292         /* used to tell cpu_init() that it can proceed with initialization */
 293         cpumask_set_cpu(cpu, cpu_callout_mask);
 294         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 295                 return 0;
 296
 297         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 298         if (ctxt == NULL)
 299                 return -ENOMEM;
 300
 301         gdt = get_cpu_gdt_rw(cpu);
 302
 303 #ifdef CONFIG_X86_32
 304         ctxt->user_regs.fs = __KERNEL_PERCPU;
 305         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 306 #endif
 307         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 308
 309         /*
 310          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 311          * pointing just below where pt_regs would be if it were a normal
 312          * kernel entry.
 313          */
 314         ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
 315         ctxt->flags = VGCF_IN_KERNEL;
 316         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 317         ctxt->user_regs.ds = __USER_DS;
 318         ctxt->user_regs.es = __USER_DS;
 319         ctxt->user_regs.ss = __KERNEL_DS;
 320         ctxt->user_regs.cs = __KERNEL_CS;
 321         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 322
 323         xen_copy_trap_info(ctxt->trap_ctxt);
 324
 325         ctxt->ldt_ents = 0;
 326
 327         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 328
 329         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 330         make_lowmem_page_readonly(gdt);
 331         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 332
 333         ctxt->gdt_frames[0] = gdt_mfn;
 334         ctxt->gdt_ents      = GDT_ENTRIES;
 335
 336         /*
 337          * Set SS:SP that Xen will use when entering guest kernel mode
 338          * from guest user mode.  Subsequent calls to load_sp0() can
 339          * change this value.
 340          */
 341         ctxt->kernel_ss = __KERNEL_DS;
 342         ctxt->kernel_sp = task_top_of_stack(idle);
 343
 344 #ifdef CONFIG_X86_32
 345         ctxt->event_callback_cs     = __KERNEL_CS;
 346         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 347 #else
 348         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 349 #endif
 350         ctxt->event_callback_eip    =
 351                 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
 352         ctxt->failsafe_callback_eip =
 353                 (unsigned long)xen_failsafe_callback;
 354         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 355
 356         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 357         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 358                 BUG();
 359
 360         kfree(ctxt);
 361         return 0;
 362 }
 363
 364 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 365 {
 366         int rc;
 367
 368         rc = common_cpu_up(cpu, idle);
 369         if (rc)
 370                 return rc;
 371
 372         xen_setup_runstate_info(cpu);
 373
 374         /*
 375          * PV VCPUs are always successfully taken down (see 'while' loop
 376          * in xen_cpu_die()), so -EBUSY is an error.
 377          */
 378         rc = cpu_check_up_prepare(cpu);
 379         if (rc)
 380                 return rc;
 381
 382         /* make sure interrupts start blocked */
 383         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 384
 385         rc = cpu_initialize_context(cpu, idle);
 386         if (rc)
 387                 return rc;
 388
 389         xen_pmu_init(cpu);
 390
 391         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 392         BUG_ON(rc);
 393
 394         while (cpu_report_state(cpu) != CPU_ONLINE)
 395                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 396
 397         return 0;
 398 }
 399
 400 #ifdef CONFIG_HOTPLUG_CPU
 401 static int xen_pv_cpu_disable(void)
 402 {
 403         unsigned int cpu = smp_processor_id();
 404         if (cpu == 0)
 405                 return -EBUSY;
 406
 407         cpu_disable_common();
 408
 409         load_cr3(swapper_pg_dir);
 410         return 0;
 411 }
 412
 413 static void xen_pv_cpu_die(unsigned int cpu)
 414 {
 415         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 416                                   xen_vcpu_nr(cpu), NULL)) {
 417                 __set_current_state(TASK_UNINTERRUPTIBLE);
 418                 schedule_timeout(HZ/10);
 419         }
 420
 421         if (common_cpu_die(cpu) == 0) {
 422                 xen_smp_intr_free(cpu);
 423                 xen_uninit_lock_cpu(cpu);
 424                 xen_teardown_timer(cpu);
 425                 xen_pmu_finish(cpu);
 426         }
 427 }
 428
 429 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 430 {
 431         play_dead_common();
 432         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 433         cpu_bringup();
 434         /*
 435          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 436          * clears certain data that the cpu_idle loop (which called us
 437          * and that we return from) expects. The only way to get that
 438          * data back is to call:
 439          */
 440         tick_nohz_idle_enter();
 441         tick_nohz_idle_stop_tick_protected();
 442
 443         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 444 }
 445
 446 #else /* !CONFIG_HOTPLUG_CPU */
 447 static int xen_pv_cpu_disable(void)
 448 {
 449         return -ENOSYS;
 450 }
 451
 452 static void xen_pv_cpu_die(unsigned int cpu)
 453 {
 454         BUG();
 455 }
 456
 457 static void xen_pv_play_dead(void)
 458 {
 459         BUG();
 460 }
 461
 462 #endif
 463 static void stop_self(void *v)
 464 {
 465         int cpu = smp_processor_id();
 466
 467         /* make sure we're not pinning something down */
 468         load_cr3(swapper_pg_dir);
 469         /* should set up a minimal gdt */
 470
 471         set_cpu_online(cpu, false);
 472
 473         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 474         BUG();
 475 }
 476
 477 static void xen_pv_stop_other_cpus(int wait)
 478 {
 479         smp_call_function(stop_self, NULL, wait);
 480 }
 481
 482 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 483 {
 484         irq_enter();
 485         irq_work_run();
 486         inc_irq_stat(apic_irq_work_irqs);
 487         irq_exit();
 488
 489         return IRQ_HANDLED;
 490 }
 491
 492 static const struct smp_ops xen_smp_ops __initconst = {
 493         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 494         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 495         .smp_cpus_done = xen_smp_cpus_done,
 496
 497         .cpu_up = xen_pv_cpu_up,
 498         .cpu_die = xen_pv_cpu_die,
 499         .cpu_disable = xen_pv_cpu_disable,
 500         .play_dead = xen_pv_play_dead,
 501
 502         .stop_other_cpus = xen_pv_stop_other_cpus,
 503         .smp_send_reschedule = xen_smp_send_reschedule,
 504
 505         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 506         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 507 };
 508
 509 void __init xen_smp_init(void)
 510 {
 511         smp_ops = xen_smp_ops;
 512         xen_fill_possible_map();
 513 }