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/spec-ctrl.h>
  36 #include <asm/xen/interface.h>
  37 #include <asm/xen/hypercall.h>
  38
  39 #include <xen/xen.h>
  40 #include <xen/page.h>
  41 #include <xen/events.h>
  42
  43 #include <xen/hvc-console.h>
  44 #include "xen-ops.h"
  45 #include "mmu.h"
  46 #include "smp.h"
  47 #include "pmu.h"
  48
  49 cpumask_var_t xen_cpu_initialized_map;
  50
  51 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  52 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  53
  54 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  55
  56 static void cpu_bringup(void)
  57 {
  58         int cpu;
  59
  60         cpu_init();
  61         touch_softlockup_watchdog();
  62         preempt_disable();
  63
  64         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  65         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  66                 xen_enable_sysenter();
  67                 xen_enable_syscall();
  68         }
  69         cpu = smp_processor_id();
  70         smp_store_cpu_info(cpu);
  71         cpu_data(cpu).x86_max_cores = 1;
  72         set_cpu_sibling_map(cpu);
  73
  74         speculative_store_bypass_ht_init();
  75
  76         xen_setup_cpu_clockevents();
  77
  78         notify_cpu_starting(cpu);
  79
  80         set_cpu_online(cpu, true);
  81
  82         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  83
  84         /* We can take interrupts now: we're officially "up". */
  85         local_irq_enable();
  86 }
  87
  88 asmlinkage __visible void cpu_bringup_and_idle(void)
  89 {
  90         cpu_bringup();
  91         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  92 }
  93
  94 void xen_smp_intr_free_pv(unsigned int cpu)
  95 {
  96         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
  97                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
  98                 per_cpu(xen_irq_work, cpu).irq = -1;
  99                 kfree(per_cpu(xen_irq_work, cpu).name);
 100                 per_cpu(xen_irq_work, cpu).name = NULL;
 101         }
 102
 103         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 104                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 105                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 106                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 107                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 108         }
 109 }
 110
 111 int xen_smp_intr_init_pv(unsigned int cpu)
 112 {
 113         int rc;
 114         char *callfunc_name, *pmu_name;
 115
 116         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 117         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 118                                     cpu,
 119                                     xen_irq_work_interrupt,
 120                                     IRQF_PERCPU|IRQF_NOBALANCING,
 121                                     callfunc_name,
 122                                     NULL);
 123         if (rc < 0)
 124                 goto fail;
 125         per_cpu(xen_irq_work, cpu).irq = rc;
 126         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 127
 128         if (is_xen_pmu(cpu)) {
 129                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 130                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 131                                              xen_pmu_irq_handler,
 132                                              IRQF_PERCPU|IRQF_NOBALANCING,
 133                                              pmu_name, NULL);
 134                 if (rc < 0)
 135                         goto fail;
 136                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 137                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 138         }
 139
 140         return 0;
 141
 142  fail:
 143         xen_smp_intr_free_pv(cpu);
 144         return rc;
 145 }
 146
 147 static void __init xen_fill_possible_map(void)
 148 {
 149         int i, rc;
 150
 151         if (xen_initial_domain())
 152                 return;
 153
 154         for (i = 0; i < nr_cpu_ids; i++) {
 155                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 156                 if (rc >= 0) {
 157                         num_processors++;
 158                         set_cpu_possible(i, true);
 159                 }
 160         }
 161 }
 162
 163 static void __init xen_filter_cpu_maps(void)
 164 {
 165         int i, rc;
 166         unsigned int subtract = 0;
 167
 168         if (!xen_initial_domain())
 169                 return;
 170
 171         num_processors = 0;
 172         disabled_cpus = 0;
 173         for (i = 0; i < nr_cpu_ids; i++) {
 174                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 175                 if (rc >= 0) {
 176                         num_processors++;
 177                         set_cpu_possible(i, true);
 178                 } else {
 179                         set_cpu_possible(i, false);
 180                         set_cpu_present(i, false);
 181                         subtract++;
 182                 }
 183         }
 184 #ifdef CONFIG_HOTPLUG_CPU
 185         /* This is akin to using 'nr_cpus' on the Linux command line.
 186          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 187          * have up to X, while nr_cpu_ids is greater than X. This
 188          * normally is not a problem, except when CPU hotplugging
 189          * is involved and then there might be more than X CPUs
 190          * in the guest - which will not work as there is no
 191          * hypercall to expand the max number of VCPUs an already
 192          * running guest has. So cap it up to X. */
 193         if (subtract)
 194                 nr_cpu_ids = nr_cpu_ids - subtract;
 195 #endif
 196
 197 }
 198
 199 static void __init xen_pv_smp_prepare_boot_cpu(void)
 200 {
 201         BUG_ON(smp_processor_id() != 0);
 202         native_smp_prepare_boot_cpu();
 203
 204         if (!xen_feature(XENFEAT_writable_page_tables))
 205                 /* We've switched to the "real" per-cpu gdt, so make
 206                  * sure the old memory can be recycled. */
 207                 make_lowmem_page_readwrite(xen_initial_gdt);
 208
 209 #ifdef CONFIG_X86_32
 210         /*
 211          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 212          * expects __USER_DS
 213          */
 214         loadsegment(ds, __USER_DS);
 215         loadsegment(es, __USER_DS);
 216 #endif
 217
 218         xen_filter_cpu_maps();
 219         xen_setup_vcpu_info_placement();
 220
 221         /*
 222          * The alternative logic (which patches the unlock/lock) runs before
 223          * the smp bootup up code is activated. Hence we need to set this up
 224          * the core kernel is being patched. Otherwise we will have only
 225          * modules patched but not core code.
 226          */
 227         xen_init_spinlocks();
 228 }
 229
 230 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 231 {
 232         unsigned cpu;
 233         unsigned int i;
 234
 235         if (skip_ioapic_setup) {
 236                 char *m = (max_cpus == 0) ?
 237                         "The nosmp parameter is incompatible with Xen; " \
 238                         "use Xen dom0_max_vcpus=1 parameter" :
 239                         "The noapic parameter is incompatible with Xen";
 240
 241                 xen_raw_printk(m);
 242                 panic(m);
 243         }
 244         xen_init_lock_cpu(0);
 245
 246         smp_store_boot_cpu_info();
 247         cpu_data(0).x86_max_cores = 1;
 248
 249         for_each_possible_cpu(i) {
 250                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 251                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 252                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 253         }
 254         set_cpu_sibling_map(0);
 255
 256         speculative_store_bypass_ht_init();
 257
 258         xen_pmu_init(0);
 259
 260         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 261                 BUG();
 262
 263         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 264                 panic("could not allocate xen_cpu_initialized_map\n");
 265
 266         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 267
 268         /* Restrict the possible_map according to max_cpus. */
 269         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 270                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 271                         continue;
 272                 set_cpu_possible(cpu, false);
 273         }
 274
 275         for_each_possible_cpu(cpu)
 276                 set_cpu_present(cpu, true);
 277 }
 278
 279 static int
 280 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 281 {
 282         struct vcpu_guest_context *ctxt;
 283         struct desc_struct *gdt;
 284         unsigned long gdt_mfn;
 285
 286         /* used to tell cpu_init() that it can proceed with initialization */
 287         cpumask_set_cpu(cpu, cpu_callout_mask);
 288         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 289                 return 0;
 290
 291         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 292         if (ctxt == NULL)
 293                 return -ENOMEM;
 294
 295         gdt = get_cpu_gdt_rw(cpu);
 296
 297 #ifdef CONFIG_X86_32
 298         ctxt->user_regs.fs = __KERNEL_PERCPU;
 299         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 300 #endif
 301         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 302
 303         /*
 304          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 305          * pointing just below where pt_regs would be if it were a normal
 306          * kernel entry.
 307          */
 308         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 309         ctxt->flags = VGCF_IN_KERNEL;
 310         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 311         ctxt->user_regs.ds = __USER_DS;
 312         ctxt->user_regs.es = __USER_DS;
 313         ctxt->user_regs.ss = __KERNEL_DS;
 314         ctxt->user_regs.cs = __KERNEL_CS;
 315         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 316
 317         xen_copy_trap_info(ctxt->trap_ctxt);
 318
 319         ctxt->ldt_ents = 0;
 320
 321         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 322
 323         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 324         make_lowmem_page_readonly(gdt);
 325         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 326
 327         ctxt->gdt_frames[0] = gdt_mfn;
 328         ctxt->gdt_ents      = GDT_ENTRIES;
 329
 330         /*
 331          * Set SS:SP that Xen will use when entering guest kernel mode
 332          * from guest user mode.  Subsequent calls to load_sp0() can
 333          * change this value.
 334          */
 335         ctxt->kernel_ss = __KERNEL_DS;
 336         ctxt->kernel_sp = task_top_of_stack(idle);
 337
 338 #ifdef CONFIG_X86_32
 339         ctxt->event_callback_cs     = __KERNEL_CS;
 340         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 341 #else
 342         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 343 #endif
 344         ctxt->event_callback_eip    =
 345                 (unsigned long)xen_hypervisor_callback;
 346         ctxt->failsafe_callback_eip =
 347                 (unsigned long)xen_failsafe_callback;
 348         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 349
 350         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 351         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 352                 BUG();
 353
 354         kfree(ctxt);
 355         return 0;
 356 }
 357
 358 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 359 {
 360         int rc;
 361
 362         common_cpu_up(cpu, idle);
 363
 364         xen_setup_runstate_info(cpu);
 365
 366         /*
 367          * PV VCPUs are always successfully taken down (see 'while' loop
 368          * in xen_cpu_die()), so -EBUSY is an error.
 369          */
 370         rc = cpu_check_up_prepare(cpu);
 371         if (rc)
 372                 return rc;
 373
 374         /* make sure interrupts start blocked */
 375         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 376
 377         rc = cpu_initialize_context(cpu, idle);
 378         if (rc)
 379                 return rc;
 380
 381         xen_pmu_init(cpu);
 382
 383         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 384         BUG_ON(rc);
 385
 386         while (cpu_report_state(cpu) != CPU_ONLINE)
 387                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 388
 389         return 0;
 390 }
 391
 392 #ifdef CONFIG_HOTPLUG_CPU
 393 static int xen_pv_cpu_disable(void)
 394 {
 395         unsigned int cpu = smp_processor_id();
 396         if (cpu == 0)
 397                 return -EBUSY;
 398
 399         cpu_disable_common();
 400
 401         load_cr3(swapper_pg_dir);
 402         return 0;
 403 }
 404
 405 static void xen_pv_cpu_die(unsigned int cpu)
 406 {
 407         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 408                                   xen_vcpu_nr(cpu), NULL)) {
 409                 __set_current_state(TASK_UNINTERRUPTIBLE);
 410                 schedule_timeout(HZ/10);
 411         }
 412
 413         if (common_cpu_die(cpu) == 0) {
 414                 xen_smp_intr_free(cpu);
 415                 xen_uninit_lock_cpu(cpu);
 416                 xen_teardown_timer(cpu);
 417                 xen_pmu_finish(cpu);
 418         }
 419 }
 420
 421 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 422 {
 423         play_dead_common();
 424         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 425         cpu_bringup();
 426         /*
 427          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 428          * clears certain data that the cpu_idle loop (which called us
 429          * and that we return from) expects. The only way to get that
 430          * data back is to call:
 431          */
 432         tick_nohz_idle_enter();
 433         tick_nohz_idle_stop_tick_protected();
 434
 435         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 436 }
 437
 438 #else /* !CONFIG_HOTPLUG_CPU */
 439 static int xen_pv_cpu_disable(void)
 440 {
 441         return -ENOSYS;
 442 }
 443
 444 static void xen_pv_cpu_die(unsigned int cpu)
 445 {
 446         BUG();
 447 }
 448
 449 static void xen_pv_play_dead(void)
 450 {
 451         BUG();
 452 }
 453
 454 #endif
 455 static void stop_self(void *v)
 456 {
 457         int cpu = smp_processor_id();
 458
 459         /* make sure we're not pinning something down */
 460         load_cr3(swapper_pg_dir);
 461         /* should set up a minimal gdt */
 462
 463         set_cpu_online(cpu, false);
 464
 465         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 466         BUG();
 467 }
 468
 469 static void xen_pv_stop_other_cpus(int wait)
 470 {
 471         smp_call_function(stop_self, NULL, wait);
 472 }
 473
 474 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 475 {
 476         irq_enter();
 477         irq_work_run();
 478         inc_irq_stat(apic_irq_work_irqs);
 479         irq_exit();
 480
 481         return IRQ_HANDLED;
 482 }
 483
 484 static const struct smp_ops xen_smp_ops __initconst = {
 485         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 486         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 487         .smp_cpus_done = xen_smp_cpus_done,
 488
 489         .cpu_up = xen_pv_cpu_up,
 490         .cpu_die = xen_pv_cpu_die,
 491         .cpu_disable = xen_pv_cpu_disable,
 492         .play_dead = xen_pv_play_dead,
 493
 494         .stop_other_cpus = xen_pv_stop_other_cpus,
 495         .smp_send_reschedule = xen_smp_send_reschedule,
 496
 497         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 498         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 499 };
 500
 501 void __init xen_smp_init(void)
 502 {
 503         smp_ops = xen_smp_ops;
 504         xen_fill_possible_map();
 505 }