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
  27 #include <asm/paravirt.h>
  28 #include <asm/desc.h>
  29 #include <asm/pgtable.h>
  30 #include <asm/cpu.h>
  31
  32 #include <xen/interface/xen.h>
  33 #include <xen/interface/vcpu.h>
  34 #include <xen/interface/xenpmu.h>
  35
  36 #include <asm/spec-ctrl.h>
  37 #include <asm/xen/interface.h>
  38 #include <asm/xen/hypercall.h>
  39
  40 #include <xen/xen.h>
  41 #include <xen/page.h>
  42 #include <xen/events.h>
  43
  44 #include <xen/hvc-console.h>
  45 #include "xen-ops.h"
  46 #include "mmu.h"
  47 #include "smp.h"
  48 #include "pmu.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         cpu_init();
  62         touch_softlockup_watchdog();
  63         preempt_disable();
  64
  65         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  66         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  67                 xen_enable_sysenter();
  68                 xen_enable_syscall();
  69         }
  70         cpu = smp_processor_id();
  71         smp_store_cpu_info(cpu);
  72         cpu_data(cpu).x86_max_cores = 1;
  73         set_cpu_sibling_map(cpu);
  74
  75         speculative_store_bypass_ht_init();
  76
  77         xen_setup_cpu_clockevents();
  78
  79         notify_cpu_starting(cpu);
  80
  81         set_cpu_online(cpu, true);
  82
  83         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  84
  85         /* We can take interrupts now: we're officially "up". */
  86         local_irq_enable();
  87 }
  88
  89 asmlinkage __visible void cpu_bringup_and_idle(void)
  90 {
  91         cpu_bringup();
  92         boot_init_stack_canary();
  93         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  94 }
  95
  96 void xen_smp_intr_free_pv(unsigned int cpu)
  97 {
  98         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
  99                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 100                 per_cpu(xen_irq_work, cpu).irq = -1;
 101                 kfree(per_cpu(xen_irq_work, cpu).name);
 102                 per_cpu(xen_irq_work, cpu).name = NULL;
 103         }
 104
 105         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 106                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 107                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 108                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 109                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 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         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 120                                     cpu,
 121                                     xen_irq_work_interrupt,
 122                                     IRQF_PERCPU|IRQF_NOBALANCING,
 123                                     callfunc_name,
 124                                     NULL);
 125         if (rc < 0)
 126                 goto fail;
 127         per_cpu(xen_irq_work, cpu).irq = rc;
 128         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 129
 130         if (is_xen_pmu(cpu)) {
 131                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 132                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 133                                              xen_pmu_irq_handler,
 134                                              IRQF_PERCPU|IRQF_NOBALANCING,
 135                                              pmu_name, NULL);
 136                 if (rc < 0)
 137                         goto fail;
 138                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 139                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 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_fill_possible_map(void)
 150 {
 151         int i, rc;
 152
 153         if (xen_initial_domain())
 154                 return;
 155
 156         for (i = 0; i < nr_cpu_ids; i++) {
 157                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 158                 if (rc >= 0) {
 159                         num_processors++;
 160                         set_cpu_possible(i, true);
 161                 }
 162         }
 163 }
 164
 165 static void __init xen_filter_cpu_maps(void)
 166 {
 167         int i, rc;
 168         unsigned int subtract = 0;
 169
 170         if (!xen_initial_domain())
 171                 return;
 172
 173         num_processors = 0;
 174         disabled_cpus = 0;
 175         for (i = 0; i < nr_cpu_ids; i++) {
 176                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 177                 if (rc >= 0) {
 178                         num_processors++;
 179                         set_cpu_possible(i, true);
 180                 } else {
 181                         set_cpu_possible(i, false);
 182                         set_cpu_present(i, false);
 183                         subtract++;
 184                 }
 185         }
 186 #ifdef CONFIG_HOTPLUG_CPU
 187         /* This is akin to using 'nr_cpus' on the Linux command line.
 188          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 189          * have up to X, while nr_cpu_ids is greater than X. This
 190          * normally is not a problem, except when CPU hotplugging
 191          * is involved and then there might be more than X CPUs
 192          * in the guest - which will not work as there is no
 193          * hypercall to expand the max number of VCPUs an already
 194          * running guest has. So cap it up to X. */
 195         if (subtract)
 196                 nr_cpu_ids = nr_cpu_ids - subtract;
 197 #endif
 198
 199 }
 200
 201 static void __init xen_pv_smp_prepare_boot_cpu(void)
 202 {
 203         BUG_ON(smp_processor_id() != 0);
 204         native_smp_prepare_boot_cpu();
 205
 206         if (!xen_feature(XENFEAT_writable_page_tables))
 207                 /* We've switched to the "real" per-cpu gdt, so make
 208                  * sure the old memory can be recycled. */
 209                 make_lowmem_page_readwrite(xen_initial_gdt);
 210
 211 #ifdef CONFIG_X86_32
 212         /*
 213          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 214          * expects __USER_DS
 215          */
 216         loadsegment(ds, __USER_DS);
 217         loadsegment(es, __USER_DS);
 218 #endif
 219
 220         xen_filter_cpu_maps();
 221         xen_setup_vcpu_info_placement();
 222
 223         /*
 224          * The alternative logic (which patches the unlock/lock) runs before
 225          * the smp bootup up code is activated. Hence we need to set this up
 226          * the core kernel is being patched. Otherwise we will have only
 227          * modules patched but not core code.
 228          */
 229         xen_init_spinlocks();
 230 }
 231
 232 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 233 {
 234         unsigned cpu;
 235         unsigned int i;
 236
 237         if (skip_ioapic_setup) {
 238                 char *m = (max_cpus == 0) ?
 239                         "The nosmp parameter is incompatible with Xen; " \
 240                         "use Xen dom0_max_vcpus=1 parameter" :
 241                         "The noapic parameter is incompatible with Xen";
 242
 243                 xen_raw_printk(m);
 244                 panic(m);
 245         }
 246         xen_init_lock_cpu(0);
 247
 248         smp_store_boot_cpu_info();
 249         cpu_data(0).x86_max_cores = 1;
 250
 251         for_each_possible_cpu(i) {
 252                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 253                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 254                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 255         }
 256         set_cpu_sibling_map(0);
 257
 258         speculative_store_bypass_ht_init();
 259
 260         xen_pmu_init(0);
 261
 262         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 263                 BUG();
 264
 265         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 266                 panic("could not allocate xen_cpu_initialized_map\n");
 267
 268         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 269
 270         /* Restrict the possible_map according to max_cpus. */
 271         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 272                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 273                         continue;
 274                 set_cpu_possible(cpu, false);
 275         }
 276
 277         for_each_possible_cpu(cpu)
 278                 set_cpu_present(cpu, true);
 279 }
 280
 281 static int
 282 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 283 {
 284         struct vcpu_guest_context *ctxt;
 285         struct desc_struct *gdt;
 286         unsigned long gdt_mfn;
 287
 288         /* used to tell cpu_init() that it can proceed with initialization */
 289         cpumask_set_cpu(cpu, cpu_callout_mask);
 290         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 291                 return 0;
 292
 293         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 294         if (ctxt == NULL)
 295                 return -ENOMEM;
 296
 297         gdt = get_cpu_gdt_rw(cpu);
 298
 299 #ifdef CONFIG_X86_32
 300         ctxt->user_regs.fs = __KERNEL_PERCPU;
 301         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 302 #endif
 303         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 304
 305         /*
 306          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 307          * pointing just below where pt_regs would be if it were a normal
 308          * kernel entry.
 309          */
 310         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 311         ctxt->flags = VGCF_IN_KERNEL;
 312         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 313         ctxt->user_regs.ds = __USER_DS;
 314         ctxt->user_regs.es = __USER_DS;
 315         ctxt->user_regs.ss = __KERNEL_DS;
 316         ctxt->user_regs.cs = __KERNEL_CS;
 317         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 318
 319         xen_copy_trap_info(ctxt->trap_ctxt);
 320
 321         ctxt->ldt_ents = 0;
 322
 323         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 324
 325         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 326         make_lowmem_page_readonly(gdt);
 327         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 328
 329         ctxt->gdt_frames[0] = gdt_mfn;
 330         ctxt->gdt_ents      = GDT_ENTRIES;
 331
 332         /*
 333          * Set SS:SP that Xen will use when entering guest kernel mode
 334          * from guest user mode.  Subsequent calls to load_sp0() can
 335          * change this value.
 336          */
 337         ctxt->kernel_ss = __KERNEL_DS;
 338         ctxt->kernel_sp = task_top_of_stack(idle);
 339
 340 #ifdef CONFIG_X86_32
 341         ctxt->event_callback_cs     = __KERNEL_CS;
 342         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 343 #else
 344         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 345 #endif
 346         ctxt->event_callback_eip    =
 347                 (unsigned long)xen_hypervisor_callback;
 348         ctxt->failsafe_callback_eip =
 349                 (unsigned long)xen_failsafe_callback;
 350         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 351
 352         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 353         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 354                 BUG();
 355
 356         kfree(ctxt);
 357         return 0;
 358 }
 359
 360 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 361 {
 362         int rc;
 363
 364         common_cpu_up(cpu, idle);
 365
 366         xen_setup_runstate_info(cpu);
 367
 368         /*
 369          * PV VCPUs are always successfully taken down (see 'while' loop
 370          * in xen_cpu_die()), so -EBUSY is an error.
 371          */
 372         rc = cpu_check_up_prepare(cpu);
 373         if (rc)
 374                 return rc;
 375
 376         /* make sure interrupts start blocked */
 377         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 378
 379         rc = cpu_initialize_context(cpu, idle);
 380         if (rc)
 381                 return rc;
 382
 383         xen_pmu_init(cpu);
 384
 385         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 386         BUG_ON(rc);
 387
 388         while (cpu_report_state(cpu) != CPU_ONLINE)
 389                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 390
 391         return 0;
 392 }
 393
 394 #ifdef CONFIG_HOTPLUG_CPU
 395 static int xen_pv_cpu_disable(void)
 396 {
 397         unsigned int cpu = smp_processor_id();
 398         if (cpu == 0)
 399                 return -EBUSY;
 400
 401         cpu_disable_common();
 402
 403         load_cr3(swapper_pg_dir);
 404         return 0;
 405 }
 406
 407 static void xen_pv_cpu_die(unsigned int cpu)
 408 {
 409         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 410                                   xen_vcpu_nr(cpu), NULL)) {
 411                 __set_current_state(TASK_UNINTERRUPTIBLE);
 412                 schedule_timeout(HZ/10);
 413         }
 414
 415         if (common_cpu_die(cpu) == 0) {
 416                 xen_smp_intr_free(cpu);
 417                 xen_uninit_lock_cpu(cpu);
 418                 xen_teardown_timer(cpu);
 419                 xen_pmu_finish(cpu);
 420         }
 421 }
 422
 423 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 424 {
 425         play_dead_common();
 426         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 427         cpu_bringup();
 428         /*
 429          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 430          * clears certain data that the cpu_idle loop (which called us
 431          * and that we return from) expects. The only way to get that
 432          * data back is to call:
 433          */
 434         tick_nohz_idle_enter();
 435         tick_nohz_idle_stop_tick_protected();
 436
 437         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 438 }
 439
 440 #else /* !CONFIG_HOTPLUG_CPU */
 441 static int xen_pv_cpu_disable(void)
 442 {
 443         return -ENOSYS;
 444 }
 445
 446 static void xen_pv_cpu_die(unsigned int cpu)
 447 {
 448         BUG();
 449 }
 450
 451 static void xen_pv_play_dead(void)
 452 {
 453         BUG();
 454 }
 455
 456 #endif
 457 static void stop_self(void *v)
 458 {
 459         int cpu = smp_processor_id();
 460
 461         /* make sure we're not pinning something down */
 462         load_cr3(swapper_pg_dir);
 463         /* should set up a minimal gdt */
 464
 465         set_cpu_online(cpu, false);
 466
 467         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 468         BUG();
 469 }
 470
 471 static void xen_pv_stop_other_cpus(int wait)
 472 {
 473         smp_call_function(stop_self, NULL, wait);
 474 }
 475
 476 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 477 {
 478         irq_enter();
 479         irq_work_run();
 480         inc_irq_stat(apic_irq_work_irqs);
 481         irq_exit();
 482
 483         return IRQ_HANDLED;
 484 }
 485
 486 static const struct smp_ops xen_smp_ops __initconst = {
 487         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 488         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 489         .smp_cpus_done = xen_smp_cpus_done,
 490
 491         .cpu_up = xen_pv_cpu_up,
 492         .cpu_die = xen_pv_cpu_die,
 493         .cpu_disable = xen_pv_cpu_disable,
 494         .play_dead = xen_pv_play_dead,
 495
 496         .stop_other_cpus = xen_pv_stop_other_cpus,
 497         .smp_send_reschedule = xen_smp_send_reschedule,
 498
 499         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 500         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 501 };
 502
 503 void __init xen_smp_init(void)
 504 {
 505         smp_ops = xen_smp_ops;
 506         xen_fill_possible_map();
 507 }