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         prevent_tail_call_optimization();
  93 }
  94
  95 void xen_smp_intr_free_pv(unsigned int cpu)
  96 {
  97         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
  98                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
  99                 per_cpu(xen_irq_work, cpu).irq = -1;
 100                 kfree(per_cpu(xen_irq_work, cpu).name);
 101                 per_cpu(xen_irq_work, cpu).name = NULL;
 102         }
 103
 104         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 105                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 106                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 107                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 108                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 109         }
 110 }
 111
 112 int xen_smp_intr_init_pv(unsigned int cpu)
 113 {
 114         int rc;
 115         char *callfunc_name, *pmu_name;
 116
 117         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 118         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 119                                     cpu,
 120                                     xen_irq_work_interrupt,
 121                                     IRQF_PERCPU|IRQF_NOBALANCING,
 122                                     callfunc_name,
 123                                     NULL);
 124         if (rc < 0)
 125                 goto fail;
 126         per_cpu(xen_irq_work, cpu).irq = rc;
 127         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 128
 129         if (is_xen_pmu) {
 130                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 131                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 132                                              xen_pmu_irq_handler,
 133                                              IRQF_PERCPU|IRQF_NOBALANCING,
 134                                              pmu_name, NULL);
 135                 if (rc < 0)
 136                         goto fail;
 137                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 138                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 139         }
 140
 141         return 0;
 142
 143  fail:
 144         xen_smp_intr_free_pv(cpu);
 145         return rc;
 146 }
 147
 148 static void __init xen_fill_possible_map(void)
 149 {
 150         int i, rc;
 151
 152         if (xen_initial_domain())
 153                 return;
 154
 155         for (i = 0; i < nr_cpu_ids; i++) {
 156                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 157                 if (rc >= 0) {
 158                         num_processors++;
 159                         set_cpu_possible(i, true);
 160                 }
 161         }
 162 }
 163
 164 static void __init xen_filter_cpu_maps(void)
 165 {
 166         int i, rc;
 167         unsigned int subtract = 0;
 168
 169         if (!xen_initial_domain())
 170                 return;
 171
 172         num_processors = 0;
 173         disabled_cpus = 0;
 174         for (i = 0; i < nr_cpu_ids; i++) {
 175                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 176                 if (rc >= 0) {
 177                         num_processors++;
 178                         set_cpu_possible(i, true);
 179                 } else {
 180                         set_cpu_possible(i, false);
 181                         set_cpu_present(i, false);
 182                         subtract++;
 183                 }
 184         }
 185 #ifdef CONFIG_HOTPLUG_CPU
 186         /* This is akin to using 'nr_cpus' on the Linux command line.
 187          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 188          * have up to X, while nr_cpu_ids is greater than X. This
 189          * normally is not a problem, except when CPU hotplugging
 190          * is involved and then there might be more than X CPUs
 191          * in the guest - which will not work as there is no
 192          * hypercall to expand the max number of VCPUs an already
 193          * running guest has. So cap it up to X. */
 194         if (subtract)
 195                 nr_cpu_ids = nr_cpu_ids - subtract;
 196 #endif
 197
 198 }
 199
 200 static void __init xen_pv_smp_prepare_boot_cpu(void)
 201 {
 202         BUG_ON(smp_processor_id() != 0);
 203         native_smp_prepare_boot_cpu();
 204
 205         if (!xen_feature(XENFEAT_writable_page_tables))
 206                 /* We've switched to the "real" per-cpu gdt, so make
 207                  * sure the old memory can be recycled. */
 208                 make_lowmem_page_readwrite(xen_initial_gdt);
 209
 210 #ifdef CONFIG_X86_32
 211         /*
 212          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 213          * expects __USER_DS
 214          */
 215         loadsegment(ds, __USER_DS);
 216         loadsegment(es, __USER_DS);
 217 #endif
 218
 219         xen_filter_cpu_maps();
 220         xen_setup_vcpu_info_placement();
 221
 222         /*
 223          * The alternative logic (which patches the unlock/lock) runs before
 224          * the smp bootup up code is activated. Hence we need to set this up
 225          * the core kernel is being patched. Otherwise we will have only
 226          * modules patched but not core code.
 227          */
 228         xen_init_spinlocks();
 229 }
 230
 231 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 232 {
 233         unsigned cpu;
 234         unsigned int i;
 235
 236         if (skip_ioapic_setup) {
 237                 char *m = (max_cpus == 0) ?
 238                         "The nosmp parameter is incompatible with Xen; " \
 239                         "use Xen dom0_max_vcpus=1 parameter" :
 240                         "The noapic parameter is incompatible with Xen";
 241
 242                 xen_raw_printk(m);
 243                 panic(m);
 244         }
 245         xen_init_lock_cpu(0);
 246
 247         smp_store_boot_cpu_info();
 248         cpu_data(0).x86_max_cores = 1;
 249
 250         for_each_possible_cpu(i) {
 251                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 252                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 253                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 254         }
 255         set_cpu_sibling_map(0);
 256
 257         speculative_store_bypass_ht_init();
 258
 259         xen_pmu_init(0);
 260
 261         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 262                 BUG();
 263
 264         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 265                 panic("could not allocate xen_cpu_initialized_map\n");
 266
 267         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 268
 269         /* Restrict the possible_map according to max_cpus. */
 270         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 271                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 272                         continue;
 273                 set_cpu_possible(cpu, false);
 274         }
 275
 276         for_each_possible_cpu(cpu)
 277                 set_cpu_present(cpu, true);
 278 }
 279
 280 static int
 281 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 282 {
 283         struct vcpu_guest_context *ctxt;
 284         struct desc_struct *gdt;
 285         unsigned long gdt_mfn;
 286
 287         /* used to tell cpu_init() that it can proceed with initialization */
 288         cpumask_set_cpu(cpu, cpu_callout_mask);
 289         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 290                 return 0;
 291
 292         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 293         if (ctxt == NULL)
 294                 return -ENOMEM;
 295
 296         gdt = get_cpu_gdt_rw(cpu);
 297
 298 #ifdef CONFIG_X86_32
 299         ctxt->user_regs.fs = __KERNEL_PERCPU;
 300         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 301 #endif
 302         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 303
 304         /*
 305          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 306          * pointing just below where pt_regs would be if it were a normal
 307          * kernel entry.
 308          */
 309         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 310         ctxt->flags = VGCF_IN_KERNEL;
 311         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 312         ctxt->user_regs.ds = __USER_DS;
 313         ctxt->user_regs.es = __USER_DS;
 314         ctxt->user_regs.ss = __KERNEL_DS;
 315         ctxt->user_regs.cs = __KERNEL_CS;
 316         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 317
 318         xen_copy_trap_info(ctxt->trap_ctxt);
 319
 320         ctxt->ldt_ents = 0;
 321
 322         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 323
 324         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 325         make_lowmem_page_readonly(gdt);
 326         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 327
 328         ctxt->gdt_frames[0] = gdt_mfn;
 329         ctxt->gdt_ents      = GDT_ENTRIES;
 330
 331         /*
 332          * Set SS:SP that Xen will use when entering guest kernel mode
 333          * from guest user mode.  Subsequent calls to load_sp0() can
 334          * change this value.
 335          */
 336         ctxt->kernel_ss = __KERNEL_DS;
 337         ctxt->kernel_sp = task_top_of_stack(idle);
 338
 339 #ifdef CONFIG_X86_32
 340         ctxt->event_callback_cs     = __KERNEL_CS;
 341         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 342 #else
 343         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 344 #endif
 345         ctxt->event_callback_eip    =
 346                 (unsigned long)xen_hypervisor_callback;
 347         ctxt->failsafe_callback_eip =
 348                 (unsigned long)xen_failsafe_callback;
 349         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 350
 351         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 352         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 353                 BUG();
 354
 355         kfree(ctxt);
 356         return 0;
 357 }
 358
 359 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 360 {
 361         int rc;
 362
 363         common_cpu_up(cpu, idle);
 364
 365         xen_setup_runstate_info(cpu);
 366
 367         /*
 368          * PV VCPUs are always successfully taken down (see 'while' loop
 369          * in xen_cpu_die()), so -EBUSY is an error.
 370          */
 371         rc = cpu_check_up_prepare(cpu);
 372         if (rc)
 373                 return rc;
 374
 375         /* make sure interrupts start blocked */
 376         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 377
 378         rc = cpu_initialize_context(cpu, idle);
 379         if (rc)
 380                 return rc;
 381
 382         xen_pmu_init(cpu);
 383
 384         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 385         BUG_ON(rc);
 386
 387         while (cpu_report_state(cpu) != CPU_ONLINE)
 388                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 389
 390         return 0;
 391 }
 392
 393 #ifdef CONFIG_HOTPLUG_CPU
 394 static int xen_pv_cpu_disable(void)
 395 {
 396         unsigned int cpu = smp_processor_id();
 397         if (cpu == 0)
 398                 return -EBUSY;
 399
 400         cpu_disable_common();
 401
 402         load_cr3(swapper_pg_dir);
 403         return 0;
 404 }
 405
 406 static void xen_pv_cpu_die(unsigned int cpu)
 407 {
 408         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 409                                   xen_vcpu_nr(cpu), NULL)) {
 410                 __set_current_state(TASK_UNINTERRUPTIBLE);
 411                 schedule_timeout(HZ/10);
 412         }
 413
 414         if (common_cpu_die(cpu) == 0) {
 415                 xen_smp_intr_free(cpu);
 416                 xen_uninit_lock_cpu(cpu);
 417                 xen_teardown_timer(cpu);
 418                 xen_pmu_finish(cpu);
 419         }
 420 }
 421
 422 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 423 {
 424         play_dead_common();
 425         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 426         cpu_bringup();
 427         /*
 428          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 429          * clears certain data that the cpu_idle loop (which called us
 430          * and that we return from) expects. The only way to get that
 431          * data back is to call:
 432          */
 433         tick_nohz_idle_enter();
 434         tick_nohz_idle_stop_tick_protected();
 435
 436         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 437 }
 438
 439 #else /* !CONFIG_HOTPLUG_CPU */
 440 static int xen_pv_cpu_disable(void)
 441 {
 442         return -ENOSYS;
 443 }
 444
 445 static void xen_pv_cpu_die(unsigned int cpu)
 446 {
 447         BUG();
 448 }
 449
 450 static void xen_pv_play_dead(void)
 451 {
 452         BUG();
 453 }
 454
 455 #endif
 456 static void stop_self(void *v)
 457 {
 458         int cpu = smp_processor_id();
 459
 460         /* make sure we're not pinning something down */
 461         load_cr3(swapper_pg_dir);
 462         /* should set up a minimal gdt */
 463
 464         set_cpu_online(cpu, false);
 465
 466         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 467         BUG();
 468 }
 469
 470 static void xen_pv_stop_other_cpus(int wait)
 471 {
 472         smp_call_function(stop_self, NULL, wait);
 473 }
 474
 475 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 476 {
 477         irq_enter();
 478         irq_work_run();
 479         inc_irq_stat(apic_irq_work_irqs);
 480         irq_exit();
 481
 482         return IRQ_HANDLED;
 483 }
 484
 485 static const struct smp_ops xen_smp_ops __initconst = {
 486         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 487         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 488         .smp_cpus_done = xen_smp_cpus_done,
 489
 490         .cpu_up = xen_pv_cpu_up,
 491         .cpu_die = xen_pv_cpu_die,
 492         .cpu_disable = xen_pv_cpu_disable,
 493         .play_dead = xen_pv_play_dead,
 494
 495         .stop_other_cpus = xen_pv_stop_other_cpus,
 496         .smp_send_reschedule = xen_smp_send_reschedule,
 497
 498         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 499         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 500 };
 501
 502 void __init xen_smp_init(void)
 503 {
 504         smp_ops = xen_smp_ops;
 505         xen_fill_possible_map();
 506 }