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 #include <asm/fpu/internal.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         fpu__init_cpu();
  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         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  94         prevent_tail_call_optimization();
  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) {
 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_llc_shared_map, i), GFP_KERNEL);
 256         }
 257         set_cpu_sibling_map(0);
 258
 259         speculative_store_bypass_ht_init();
 260
 261         xen_pmu_init(0);
 262
 263         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 264                 BUG();
 265
 266         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 267                 panic("could not allocate xen_cpu_initialized_map\n");
 268
 269         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 270
 271         /* Restrict the possible_map according to max_cpus. */
 272         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 273                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 274                         continue;
 275                 set_cpu_possible(cpu, false);
 276         }
 277
 278         for_each_possible_cpu(cpu)
 279                 set_cpu_present(cpu, true);
 280 }
 281
 282 static int
 283 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 284 {
 285         struct vcpu_guest_context *ctxt;
 286         struct desc_struct *gdt;
 287         unsigned long gdt_mfn;
 288
 289         /* used to tell cpu_init() that it can proceed with initialization */
 290         cpumask_set_cpu(cpu, cpu_callout_mask);
 291         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 292                 return 0;
 293
 294         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 295         if (ctxt == NULL)
 296                 return -ENOMEM;
 297
 298         gdt = get_cpu_gdt_rw(cpu);
 299
 300 #ifdef CONFIG_X86_32
 301         ctxt->user_regs.fs = __KERNEL_PERCPU;
 302         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 303 #endif
 304         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 305
 306         /*
 307          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 308          * pointing just below where pt_regs would be if it were a normal
 309          * kernel entry.
 310          */
 311         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 312         ctxt->flags = VGCF_IN_KERNEL;
 313         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 314         ctxt->user_regs.ds = __USER_DS;
 315         ctxt->user_regs.es = __USER_DS;
 316         ctxt->user_regs.ss = __KERNEL_DS;
 317         ctxt->user_regs.cs = __KERNEL_CS;
 318         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 319
 320         xen_copy_trap_info(ctxt->trap_ctxt);
 321
 322         ctxt->ldt_ents = 0;
 323
 324         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 325
 326         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 327         make_lowmem_page_readonly(gdt);
 328         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 329
 330         ctxt->gdt_frames[0] = gdt_mfn;
 331         ctxt->gdt_ents      = GDT_ENTRIES;
 332
 333         /*
 334          * Set SS:SP that Xen will use when entering guest kernel mode
 335          * from guest user mode.  Subsequent calls to load_sp0() can
 336          * change this value.
 337          */
 338         ctxt->kernel_ss = __KERNEL_DS;
 339         ctxt->kernel_sp = task_top_of_stack(idle);
 340
 341 #ifdef CONFIG_X86_32
 342         ctxt->event_callback_cs     = __KERNEL_CS;
 343         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 344 #else
 345         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 346 #endif
 347         ctxt->event_callback_eip    =
 348                 (unsigned long)xen_hypervisor_callback;
 349         ctxt->failsafe_callback_eip =
 350                 (unsigned long)xen_failsafe_callback;
 351         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 352
 353         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 354         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 355                 BUG();
 356
 357         kfree(ctxt);
 358         return 0;
 359 }
 360
 361 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 362 {
 363         int rc;
 364
 365         common_cpu_up(cpu, idle);
 366
 367         xen_setup_runstate_info(cpu);
 368
 369         /*
 370          * PV VCPUs are always successfully taken down (see 'while' loop
 371          * in xen_cpu_die()), so -EBUSY is an error.
 372          */
 373         rc = cpu_check_up_prepare(cpu);
 374         if (rc)
 375                 return rc;
 376
 377         /* make sure interrupts start blocked */
 378         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 379
 380         rc = cpu_initialize_context(cpu, idle);
 381         if (rc)
 382                 return rc;
 383
 384         xen_pmu_init(cpu);
 385
 386         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 387         BUG_ON(rc);
 388
 389         while (cpu_report_state(cpu) != CPU_ONLINE)
 390                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 391
 392         return 0;
 393 }
 394
 395 #ifdef CONFIG_HOTPLUG_CPU
 396 static int xen_pv_cpu_disable(void)
 397 {
 398         unsigned int cpu = smp_processor_id();
 399         if (cpu == 0)
 400                 return -EBUSY;
 401
 402         cpu_disable_common();
 403
 404         load_cr3(swapper_pg_dir);
 405         return 0;
 406 }
 407
 408 static void xen_pv_cpu_die(unsigned int cpu)
 409 {
 410         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 411                                   xen_vcpu_nr(cpu), NULL)) {
 412                 __set_current_state(TASK_UNINTERRUPTIBLE);
 413                 schedule_timeout(HZ/10);
 414         }
 415
 416         if (common_cpu_die(cpu) == 0) {
 417                 xen_smp_intr_free(cpu);
 418                 xen_uninit_lock_cpu(cpu);
 419                 xen_teardown_timer(cpu);
 420                 xen_pmu_finish(cpu);
 421         }
 422 }
 423
 424 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 425 {
 426         play_dead_common();
 427         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 428         cpu_bringup();
 429         /*
 430          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 431          * clears certain data that the cpu_idle loop (which called us
 432          * and that we return from) expects. The only way to get that
 433          * data back is to call:
 434          */
 435         tick_nohz_idle_enter();
 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 }