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
  26 #include <asm/paravirt.h>
  27 #include <asm/desc.h>
  28 #include <asm/pgtable.h>
  29 #include <asm/cpu.h>
  30
  31 #include <xen/interface/xen.h>
  32 #include <xen/interface/vcpu.h>
  33 #include <xen/interface/xenpmu.h>
  34
  35 #include <asm/xen/interface.h>
  36 #include <asm/xen/hypercall.h>
  37
  38 #include <xen/xen.h>
  39 #include <xen/page.h>
  40 #include <xen/events.h>
  41
  42 #include <xen/hvc-console.h>
  43 #include "xen-ops.h"
  44 #include "mmu.h"
  45 #include "smp.h"
  46 #include "pmu.h"
  47
  48 cpumask_var_t xen_cpu_initialized_map;
  49
  50 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  51 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  52
  53 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  54
  55 static void cpu_bringup(void)
  56 {
  57         int cpu;
  58
  59         cpu_init();
  60         touch_softlockup_watchdog();
  61         preempt_disable();
  62
  63         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  64         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  65                 xen_enable_sysenter();
  66                 xen_enable_syscall();
  67         }
  68         cpu = smp_processor_id();
  69         smp_store_cpu_info(cpu);
  70         cpu_data(cpu).x86_max_cores = 1;
  71         set_cpu_sibling_map(cpu);
  72
  73         xen_setup_cpu_clockevents();
  74
  75         notify_cpu_starting(cpu);
  76
  77         set_cpu_online(cpu, true);
  78
  79         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  80
  81         /* We can take interrupts now: we're officially "up". */
  82         local_irq_enable();
  83 }
  84
  85 asmlinkage __visible void cpu_bringup_and_idle(void)
  86 {
  87         cpu_bringup();
  88         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  89 }
  90
  91 void xen_smp_intr_free_pv(unsigned int cpu)
  92 {
  93         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
  94                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
  95                 per_cpu(xen_irq_work, cpu).irq = -1;
  96                 kfree(per_cpu(xen_irq_work, cpu).name);
  97                 per_cpu(xen_irq_work, cpu).name = NULL;
  98         }
  99
 100         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 101                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 102                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 103                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 104                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 105         }
 106 }
 107
 108 int xen_smp_intr_init_pv(unsigned int cpu)
 109 {
 110         int rc;
 111         char *callfunc_name, *pmu_name;
 112
 113         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 114         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 115                                     cpu,
 116                                     xen_irq_work_interrupt,
 117                                     IRQF_PERCPU|IRQF_NOBALANCING,
 118                                     callfunc_name,
 119                                     NULL);
 120         if (rc < 0)
 121                 goto fail;
 122         per_cpu(xen_irq_work, cpu).irq = rc;
 123         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 124
 125         if (is_xen_pmu(cpu)) {
 126                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 127                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 128                                              xen_pmu_irq_handler,
 129                                              IRQF_PERCPU|IRQF_NOBALANCING,
 130                                              pmu_name, NULL);
 131                 if (rc < 0)
 132                         goto fail;
 133                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 134                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 135         }
 136
 137         return 0;
 138
 139  fail:
 140         xen_smp_intr_free_pv(cpu);
 141         return rc;
 142 }
 143
 144 static void __init xen_fill_possible_map(void)
 145 {
 146         int i, rc;
 147
 148         if (xen_initial_domain())
 149                 return;
 150
 151         for (i = 0; i < nr_cpu_ids; i++) {
 152                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 153                 if (rc >= 0) {
 154                         num_processors++;
 155                         set_cpu_possible(i, true);
 156                 }
 157         }
 158 }
 159
 160 static void __init xen_filter_cpu_maps(void)
 161 {
 162         int i, rc;
 163         unsigned int subtract = 0;
 164
 165         if (!xen_initial_domain())
 166                 return;
 167
 168         num_processors = 0;
 169         disabled_cpus = 0;
 170         for (i = 0; i < nr_cpu_ids; i++) {
 171                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 172                 if (rc >= 0) {
 173                         num_processors++;
 174                         set_cpu_possible(i, true);
 175                 } else {
 176                         set_cpu_possible(i, false);
 177                         set_cpu_present(i, false);
 178                         subtract++;
 179                 }
 180         }
 181 #ifdef CONFIG_HOTPLUG_CPU
 182         /* This is akin to using 'nr_cpus' on the Linux command line.
 183          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 184          * have up to X, while nr_cpu_ids is greater than X. This
 185          * normally is not a problem, except when CPU hotplugging
 186          * is involved and then there might be more than X CPUs
 187          * in the guest - which will not work as there is no
 188          * hypercall to expand the max number of VCPUs an already
 189          * running guest has. So cap it up to X. */
 190         if (subtract)
 191                 nr_cpu_ids = nr_cpu_ids - subtract;
 192 #endif
 193
 194 }
 195
 196 static void __init xen_pv_smp_prepare_boot_cpu(void)
 197 {
 198         BUG_ON(smp_processor_id() != 0);
 199         native_smp_prepare_boot_cpu();
 200
 201         if (!xen_feature(XENFEAT_writable_page_tables))
 202                 /* We've switched to the "real" per-cpu gdt, so make
 203                  * sure the old memory can be recycled. */
 204                 make_lowmem_page_readwrite(xen_initial_gdt);
 205
 206 #ifdef CONFIG_X86_32
 207         /*
 208          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 209          * expects __USER_DS
 210          */
 211         loadsegment(ds, __USER_DS);
 212         loadsegment(es, __USER_DS);
 213 #endif
 214
 215         xen_filter_cpu_maps();
 216         xen_setup_vcpu_info_placement();
 217
 218         /*
 219          * The alternative logic (which patches the unlock/lock) runs before
 220          * the smp bootup up code is activated. Hence we need to set this up
 221          * the core kernel is being patched. Otherwise we will have only
 222          * modules patched but not core code.
 223          */
 224         xen_init_spinlocks();
 225 }
 226
 227 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 228 {
 229         unsigned cpu;
 230         unsigned int i;
 231
 232         if (skip_ioapic_setup) {
 233                 char *m = (max_cpus == 0) ?
 234                         "The nosmp parameter is incompatible with Xen; " \
 235                         "use Xen dom0_max_vcpus=1 parameter" :
 236                         "The noapic parameter is incompatible with Xen";
 237
 238                 xen_raw_printk(m);
 239                 panic(m);
 240         }
 241         xen_init_lock_cpu(0);
 242
 243         smp_store_boot_cpu_info();
 244         cpu_data(0).x86_max_cores = 1;
 245
 246         for_each_possible_cpu(i) {
 247                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 248                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 249                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 250         }
 251         set_cpu_sibling_map(0);
 252
 253         xen_pmu_init(0);
 254
 255         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 256                 BUG();
 257
 258         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 259                 panic("could not allocate xen_cpu_initialized_map\n");
 260
 261         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 262
 263         /* Restrict the possible_map according to max_cpus. */
 264         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 265                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 266                         continue;
 267                 set_cpu_possible(cpu, false);
 268         }
 269
 270         for_each_possible_cpu(cpu)
 271                 set_cpu_present(cpu, true);
 272 }
 273
 274 static int
 275 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 276 {
 277         struct vcpu_guest_context *ctxt;
 278         struct desc_struct *gdt;
 279         unsigned long gdt_mfn;
 280
 281         /* used to tell cpu_init() that it can proceed with initialization */
 282         cpumask_set_cpu(cpu, cpu_callout_mask);
 283         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 284                 return 0;
 285
 286         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 287         if (ctxt == NULL)
 288                 return -ENOMEM;
 289
 290         gdt = get_cpu_gdt_rw(cpu);
 291
 292 #ifdef CONFIG_X86_32
 293         ctxt->user_regs.fs = __KERNEL_PERCPU;
 294         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 295 #endif
 296         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 297
 298         /*
 299          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 300          * pointing just below where pt_regs would be if it were a normal
 301          * kernel entry.
 302          */
 303         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 304         ctxt->flags = VGCF_IN_KERNEL;
 305         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 306         ctxt->user_regs.ds = __USER_DS;
 307         ctxt->user_regs.es = __USER_DS;
 308         ctxt->user_regs.ss = __KERNEL_DS;
 309         ctxt->user_regs.cs = __KERNEL_CS;
 310         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 311
 312         xen_copy_trap_info(ctxt->trap_ctxt);
 313
 314         ctxt->ldt_ents = 0;
 315
 316         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 317
 318         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 319         make_lowmem_page_readonly(gdt);
 320         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 321
 322         ctxt->gdt_frames[0] = gdt_mfn;
 323         ctxt->gdt_ents      = GDT_ENTRIES;
 324
 325         /*
 326          * Set SS:SP that Xen will use when entering guest kernel mode
 327          * from guest user mode.  Subsequent calls to load_sp0() can
 328          * change this value.
 329          */
 330         ctxt->kernel_ss = __KERNEL_DS;
 331         ctxt->kernel_sp = task_top_of_stack(idle);
 332
 333 #ifdef CONFIG_X86_32
 334         ctxt->event_callback_cs     = __KERNEL_CS;
 335         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 336 #else
 337         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 338 #endif
 339         ctxt->event_callback_eip    =
 340                 (unsigned long)xen_hypervisor_callback;
 341         ctxt->failsafe_callback_eip =
 342                 (unsigned long)xen_failsafe_callback;
 343         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 344
 345         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 346         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 347                 BUG();
 348
 349         kfree(ctxt);
 350         return 0;
 351 }
 352
 353 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 354 {
 355         int rc;
 356
 357         common_cpu_up(cpu, idle);
 358
 359         xen_setup_runstate_info(cpu);
 360
 361         /*
 362          * PV VCPUs are always successfully taken down (see 'while' loop
 363          * in xen_cpu_die()), so -EBUSY is an error.
 364          */
 365         rc = cpu_check_up_prepare(cpu);
 366         if (rc)
 367                 return rc;
 368
 369         /* make sure interrupts start blocked */
 370         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 371
 372         rc = cpu_initialize_context(cpu, idle);
 373         if (rc)
 374                 return rc;
 375
 376         xen_pmu_init(cpu);
 377
 378         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 379         BUG_ON(rc);
 380
 381         while (cpu_report_state(cpu) != CPU_ONLINE)
 382                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 383
 384         return 0;
 385 }
 386
 387 #ifdef CONFIG_HOTPLUG_CPU
 388 static int xen_pv_cpu_disable(void)
 389 {
 390         unsigned int cpu = smp_processor_id();
 391         if (cpu == 0)
 392                 return -EBUSY;
 393
 394         cpu_disable_common();
 395
 396         load_cr3(swapper_pg_dir);
 397         return 0;
 398 }
 399
 400 static void xen_pv_cpu_die(unsigned int cpu)
 401 {
 402         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 403                                   xen_vcpu_nr(cpu), NULL)) {
 404                 __set_current_state(TASK_UNINTERRUPTIBLE);
 405                 schedule_timeout(HZ/10);
 406         }
 407
 408         if (common_cpu_die(cpu) == 0) {
 409                 xen_smp_intr_free(cpu);
 410                 xen_uninit_lock_cpu(cpu);
 411                 xen_teardown_timer(cpu);
 412                 xen_pmu_finish(cpu);
 413         }
 414 }
 415
 416 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 417 {
 418         play_dead_common();
 419         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 420         cpu_bringup();
 421         /*
 422          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 423          * clears certain data that the cpu_idle loop (which called us
 424          * and that we return from) expects. The only way to get that
 425          * data back is to call:
 426          */
 427         tick_nohz_idle_enter();
 428
 429         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 430 }
 431
 432 #else /* !CONFIG_HOTPLUG_CPU */
 433 static int xen_pv_cpu_disable(void)
 434 {
 435         return -ENOSYS;
 436 }
 437
 438 static void xen_pv_cpu_die(unsigned int cpu)
 439 {
 440         BUG();
 441 }
 442
 443 static void xen_pv_play_dead(void)
 444 {
 445         BUG();
 446 }
 447
 448 #endif
 449 static void stop_self(void *v)
 450 {
 451         int cpu = smp_processor_id();
 452
 453         /* make sure we're not pinning something down */
 454         load_cr3(swapper_pg_dir);
 455         /* should set up a minimal gdt */
 456
 457         set_cpu_online(cpu, false);
 458
 459         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 460         BUG();
 461 }
 462
 463 static void xen_pv_stop_other_cpus(int wait)
 464 {
 465         smp_call_function(stop_self, NULL, wait);
 466 }
 467
 468 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 469 {
 470         irq_enter();
 471         irq_work_run();
 472         inc_irq_stat(apic_irq_work_irqs);
 473         irq_exit();
 474
 475         return IRQ_HANDLED;
 476 }
 477
 478 static const struct smp_ops xen_smp_ops __initconst = {
 479         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 480         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 481         .smp_cpus_done = xen_smp_cpus_done,
 482
 483         .cpu_up = xen_pv_cpu_up,
 484         .cpu_die = xen_pv_cpu_die,
 485         .cpu_disable = xen_pv_cpu_disable,
 486         .play_dead = xen_pv_play_dead,
 487
 488         .stop_other_cpus = xen_pv_stop_other_cpus,
 489         .smp_send_reschedule = xen_smp_send_reschedule,
 490
 491         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 492         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 493 };
 494
 495 void __init xen_smp_init(void)
 496 {
 497         smp_ops = xen_smp_ops;
 498         xen_fill_possible_map();
 499 }