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         cr4_init();
  62         cpu_init();
  63         touch_softlockup_watchdog();
  64         preempt_disable();
  65
  66         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  67         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  68                 xen_enable_sysenter();
  69                 xen_enable_syscall();
  70         }
  71         cpu = smp_processor_id();
  72         smp_store_cpu_info(cpu);
  73         cpu_data(cpu).x86_max_cores = 1;
  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         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  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         boot_init_stack_canary();
  94         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  95 }
  96
  97 void xen_smp_intr_free_pv(unsigned int cpu)
  98 {
  99         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
 100                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 101                 per_cpu(xen_irq_work, cpu).irq = -1;
 102                 kfree(per_cpu(xen_irq_work, cpu).name);
 103                 per_cpu(xen_irq_work, cpu).name = NULL;
 104         }
 105
 106         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 107                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 108                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 109                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 110                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 111         }
 112 }
 113
 114 int xen_smp_intr_init_pv(unsigned int cpu)
 115 {
 116         int rc;
 117         char *callfunc_name, *pmu_name;
 118
 119         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 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         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 130
 131         if (is_xen_pmu(cpu)) {
 132                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 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                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 141         }
 142
 143         return 0;
 144
 145  fail:
 146         xen_smp_intr_free_pv(cpu);
 147         return rc;
 148 }
 149
 150 static void __init xen_fill_possible_map(void)
 151 {
 152         int i, rc;
 153
 154         if (xen_initial_domain())
 155                 return;
 156
 157         for (i = 0; i < nr_cpu_ids; i++) {
 158                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 159                 if (rc >= 0) {
 160                         num_processors++;
 161                         set_cpu_possible(i, true);
 162                 }
 163         }
 164 }
 165
 166 static void __init xen_filter_cpu_maps(void)
 167 {
 168         int i, rc;
 169         unsigned int subtract = 0;
 170
 171         if (!xen_initial_domain())
 172                 return;
 173
 174         num_processors = 0;
 175         disabled_cpus = 0;
 176         for (i = 0; i < nr_cpu_ids; i++) {
 177                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 178                 if (rc >= 0) {
 179                         num_processors++;
 180                         set_cpu_possible(i, true);
 181                 } else {
 182                         set_cpu_possible(i, false);
 183                         set_cpu_present(i, false);
 184                         subtract++;
 185                 }
 186         }
 187 #ifdef CONFIG_HOTPLUG_CPU
 188         /* This is akin to using 'nr_cpus' on the Linux command line.
 189          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 190          * have up to X, while nr_cpu_ids is greater than X. This
 191          * normally is not a problem, except when CPU hotplugging
 192          * is involved and then there might be more than X CPUs
 193          * in the guest - which will not work as there is no
 194          * hypercall to expand the max number of VCPUs an already
 195          * running guest has. So cap it up to X. */
 196         if (subtract)
 197                 nr_cpu_ids = nr_cpu_ids - subtract;
 198 #endif
 199
 200 }
 201
 202 static void __init xen_pv_smp_prepare_boot_cpu(void)
 203 {
 204         BUG_ON(smp_processor_id() != 0);
 205         native_smp_prepare_boot_cpu();
 206
 207         if (!xen_feature(XENFEAT_writable_page_tables))
 208                 /* We've switched to the "real" per-cpu gdt, so make
 209                  * sure the old memory can be recycled. */
 210                 make_lowmem_page_readwrite(xen_initial_gdt);
 211
 212 #ifdef CONFIG_X86_32
 213         /*
 214          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 215          * expects __USER_DS
 216          */
 217         loadsegment(ds, __USER_DS);
 218         loadsegment(es, __USER_DS);
 219 #endif
 220
 221         xen_filter_cpu_maps();
 222         xen_setup_vcpu_info_placement();
 223
 224         /*
 225          * The alternative logic (which patches the unlock/lock) runs before
 226          * the smp bootup up code is activated. Hence we need to set this up
 227          * the core kernel is being patched. Otherwise we will have only
 228          * modules patched but not core code.
 229          */
 230         xen_init_spinlocks();
 231 }
 232
 233 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 234 {
 235         unsigned cpu;
 236         unsigned int i;
 237
 238         if (skip_ioapic_setup) {
 239                 char *m = (max_cpus == 0) ?
 240                         "The nosmp parameter is incompatible with Xen; " \
 241                         "use Xen dom0_max_vcpus=1 parameter" :
 242                         "The noapic parameter is incompatible with Xen";
 243
 244                 xen_raw_printk(m);
 245                 panic(m);
 246         }
 247         xen_init_lock_cpu(0);
 248
 249         smp_store_boot_cpu_info();
 250         cpu_data(0).x86_max_cores = 1;
 251
 252         for_each_possible_cpu(i) {
 253                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 254                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 255                 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
 256                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 257         }
 258         set_cpu_sibling_map(0);
 259
 260         speculative_store_bypass_ht_init();
 261
 262         xen_pmu_init(0);
 263
 264         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 265                 BUG();
 266
 267         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 268                 panic("could not allocate xen_cpu_initialized_map\n");
 269
 270         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 271
 272         /* Restrict the possible_map according to max_cpus. */
 273         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 274                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 275                         continue;
 276                 set_cpu_possible(cpu, false);
 277         }
 278
 279         for_each_possible_cpu(cpu)
 280                 set_cpu_present(cpu, true);
 281 }
 282
 283 static int
 284 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 285 {
 286         struct vcpu_guest_context *ctxt;
 287         struct desc_struct *gdt;
 288         unsigned long gdt_mfn;
 289
 290         /* used to tell cpu_init() that it can proceed with initialization */
 291         cpumask_set_cpu(cpu, cpu_callout_mask);
 292         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 293                 return 0;
 294
 295         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 296         if (ctxt == NULL)
 297                 return -ENOMEM;
 298
 299         gdt = get_cpu_gdt_rw(cpu);
 300
 301 #ifdef CONFIG_X86_32
 302         ctxt->user_regs.fs = __KERNEL_PERCPU;
 303         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 304 #endif
 305         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 306
 307         /*
 308          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 309          * pointing just below where pt_regs would be if it were a normal
 310          * kernel entry.
 311          */
 312         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 313         ctxt->flags = VGCF_IN_KERNEL;
 314         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 315         ctxt->user_regs.ds = __USER_DS;
 316         ctxt->user_regs.es = __USER_DS;
 317         ctxt->user_regs.ss = __KERNEL_DS;
 318         ctxt->user_regs.cs = __KERNEL_CS;
 319         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 320
 321         xen_copy_trap_info(ctxt->trap_ctxt);
 322
 323         ctxt->ldt_ents = 0;
 324
 325         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 326
 327         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 328         make_lowmem_page_readonly(gdt);
 329         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 330
 331         ctxt->gdt_frames[0] = gdt_mfn;
 332         ctxt->gdt_ents      = GDT_ENTRIES;
 333
 334         /*
 335          * Set SS:SP that Xen will use when entering guest kernel mode
 336          * from guest user mode.  Subsequent calls to load_sp0() can
 337          * change this value.
 338          */
 339         ctxt->kernel_ss = __KERNEL_DS;
 340         ctxt->kernel_sp = task_top_of_stack(idle);
 341
 342 #ifdef CONFIG_X86_32
 343         ctxt->event_callback_cs     = __KERNEL_CS;
 344         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 345 #else
 346         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 347 #endif
 348         ctxt->event_callback_eip    =
 349                 (unsigned long)xen_hypervisor_callback;
 350         ctxt->failsafe_callback_eip =
 351                 (unsigned long)xen_failsafe_callback;
 352         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 353
 354         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 355         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 356                 BUG();
 357
 358         kfree(ctxt);
 359         return 0;
 360 }
 361
 362 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 363 {
 364         int rc;
 365
 366         rc = common_cpu_up(cpu, idle);
 367         if (rc)
 368                 return rc;
 369
 370         xen_setup_runstate_info(cpu);
 371
 372         /*
 373          * PV VCPUs are always successfully taken down (see 'while' loop
 374          * in xen_cpu_die()), so -EBUSY is an error.
 375          */
 376         rc = cpu_check_up_prepare(cpu);
 377         if (rc)
 378                 return rc;
 379
 380         /* make sure interrupts start blocked */
 381         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 382
 383         rc = cpu_initialize_context(cpu, idle);
 384         if (rc)
 385                 return rc;
 386
 387         xen_pmu_init(cpu);
 388
 389         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 390         BUG_ON(rc);
 391
 392         while (cpu_report_state(cpu) != CPU_ONLINE)
 393                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 394
 395         return 0;
 396 }
 397
 398 #ifdef CONFIG_HOTPLUG_CPU
 399 static int xen_pv_cpu_disable(void)
 400 {
 401         unsigned int cpu = smp_processor_id();
 402         if (cpu == 0)
 403                 return -EBUSY;
 404
 405         cpu_disable_common();
 406
 407         load_cr3(swapper_pg_dir);
 408         return 0;
 409 }
 410
 411 static void xen_pv_cpu_die(unsigned int cpu)
 412 {
 413         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 414                                   xen_vcpu_nr(cpu), NULL)) {
 415                 __set_current_state(TASK_UNINTERRUPTIBLE);
 416                 schedule_timeout(HZ/10);
 417         }
 418
 419         if (common_cpu_die(cpu) == 0) {
 420                 xen_smp_intr_free(cpu);
 421                 xen_uninit_lock_cpu(cpu);
 422                 xen_teardown_timer(cpu);
 423                 xen_pmu_finish(cpu);
 424         }
 425 }
 426
 427 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 428 {
 429         play_dead_common();
 430         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 431         cpu_bringup();
 432         /*
 433          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 434          * clears certain data that the cpu_idle loop (which called us
 435          * and that we return from) expects. The only way to get that
 436          * data back is to call:
 437          */
 438         tick_nohz_idle_enter();
 439         tick_nohz_idle_stop_tick_protected();
 440
 441         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 442 }
 443
 444 #else /* !CONFIG_HOTPLUG_CPU */
 445 static int xen_pv_cpu_disable(void)
 446 {
 447         return -ENOSYS;
 448 }
 449
 450 static void xen_pv_cpu_die(unsigned int cpu)
 451 {
 452         BUG();
 453 }
 454
 455 static void xen_pv_play_dead(void)
 456 {
 457         BUG();
 458 }
 459
 460 #endif
 461 static void stop_self(void *v)
 462 {
 463         int cpu = smp_processor_id();
 464
 465         /* make sure we're not pinning something down */
 466         load_cr3(swapper_pg_dir);
 467         /* should set up a minimal gdt */
 468
 469         set_cpu_online(cpu, false);
 470
 471         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 472         BUG();
 473 }
 474
 475 static void xen_pv_stop_other_cpus(int wait)
 476 {
 477         smp_call_function(stop_self, NULL, wait);
 478 }
 479
 480 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 481 {
 482         irq_enter();
 483         irq_work_run();
 484         inc_irq_stat(apic_irq_work_irqs);
 485         irq_exit();
 486
 487         return IRQ_HANDLED;
 488 }
 489
 490 static const struct smp_ops xen_smp_ops __initconst = {
 491         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 492         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 493         .smp_cpus_done = xen_smp_cpus_done,
 494
 495         .cpu_up = xen_pv_cpu_up,
 496         .cpu_die = xen_pv_cpu_die,
 497         .cpu_disable = xen_pv_cpu_disable,
 498         .play_dead = xen_pv_play_dead,
 499
 500         .stop_other_cpus = xen_pv_stop_other_cpus,
 501         .smp_send_reschedule = xen_smp_send_reschedule,
 502
 503         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 504         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 505 };
 506
 507 void __init xen_smp_init(void)
 508 {
 509         smp_ops = xen_smp_ops;
 510         xen_fill_possible_map();
 511 }