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 #include <linux/pgtable.h>
  27
  28 #include <asm/paravirt.h>
  29 #include <asm/idtentry.h>
  30 #include <asm/desc.h>
  31 #include <asm/cpu.h>
  32 #include <asm/io_apic.h>
  33 #include <asm/fpu/internal.h>
  34
  35 #include <xen/interface/xen.h>
  36 #include <xen/interface/vcpu.h>
  37 #include <xen/interface/xenpmu.h>
  38
  39 #include <asm/spec-ctrl.h>
  40 #include <asm/xen/interface.h>
  41 #include <asm/xen/hypercall.h>
  42
  43 #include <xen/xen.h>
  44 #include <xen/page.h>
  45 #include <xen/events.h>
  46
  47 #include <xen/hvc-console.h>
  48 #include "xen-ops.h"
  49 #include "mmu.h"
  50 #include "smp.h"
  51 #include "pmu.h"
  52
  53 cpumask_var_t xen_cpu_initialized_map;
  54
  55 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  56 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  57
  58 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  59 void asm_cpu_bringup_and_idle(void);
  60
  61 static void cpu_bringup(void)
  62 {
  63         int cpu;
  64
  65         cr4_init();
  66         cpu_init();
  67         fpu__init_cpu();
  68         touch_softlockup_watchdog();
  69
  70         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  71         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  72                 xen_enable_sysenter();
  73                 xen_enable_syscall();
  74         }
  75         cpu = smp_processor_id();
  76         smp_store_cpu_info(cpu);
  77         cpu_data(cpu).x86_max_cores = 1;
  78         set_cpu_sibling_map(cpu);
  79
  80         speculative_store_bypass_ht_init();
  81
  82         xen_setup_cpu_clockevents();
  83
  84         notify_cpu_starting(cpu);
  85
  86         set_cpu_online(cpu, true);
  87
  88         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  89
  90         /* We can take interrupts now: we're officially "up". */
  91         local_irq_enable();
  92 }
  93
  94 asmlinkage __visible void cpu_bringup_and_idle(void)
  95 {
  96         cpu_bringup();
  97         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  98 }
  99
 100 void xen_smp_intr_free_pv(unsigned int cpu)
 101 {
 102         kfree(per_cpu(xen_irq_work, cpu).name);
 103         per_cpu(xen_irq_work, cpu).name = NULL;
 104         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
 105                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 106                 per_cpu(xen_irq_work, cpu).irq = -1;
 107         }
 108
 109         kfree(per_cpu(xen_pmu_irq, cpu).name);
 110         per_cpu(xen_pmu_irq, cpu).name = NULL;
 111         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 112                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 113                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 114         }
 115 }
 116
 117 int xen_smp_intr_init_pv(unsigned int cpu)
 118 {
 119         int rc;
 120         char *callfunc_name, *pmu_name;
 121
 122         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 123         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 124         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 125                                     cpu,
 126                                     xen_irq_work_interrupt,
 127                                     IRQF_PERCPU|IRQF_NOBALANCING,
 128                                     callfunc_name,
 129                                     NULL);
 130         if (rc < 0)
 131                 goto fail;
 132         per_cpu(xen_irq_work, cpu).irq = rc;
 133
 134         if (is_xen_pmu) {
 135                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 136                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 137                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 138                                              xen_pmu_irq_handler,
 139                                              IRQF_PERCPU|IRQF_NOBALANCING,
 140                                              pmu_name, NULL);
 141                 if (rc < 0)
 142                         goto fail;
 143                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 144         }
 145
 146         return 0;
 147
 148  fail:
 149         xen_smp_intr_free_pv(cpu);
 150         return rc;
 151 }
 152
 153 static void __init _get_smp_config(unsigned int early)
 154 {
 155         int i, rc;
 156         unsigned int subtract = 0;
 157
 158         if (early)
 159                 return;
 160
 161         num_processors = 0;
 162         disabled_cpus = 0;
 163         for (i = 0; i < nr_cpu_ids; i++) {
 164                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 165                 if (rc >= 0) {
 166                         num_processors++;
 167                         set_cpu_possible(i, true);
 168                 } else {
 169                         set_cpu_possible(i, false);
 170                         set_cpu_present(i, false);
 171                         subtract++;
 172                 }
 173         }
 174 #ifdef CONFIG_HOTPLUG_CPU
 175         /* This is akin to using 'nr_cpus' on the Linux command line.
 176          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 177          * have up to X, while nr_cpu_ids is greater than X. This
 178          * normally is not a problem, except when CPU hotplugging
 179          * is involved and then there might be more than X CPUs
 180          * in the guest - which will not work as there is no
 181          * hypercall to expand the max number of VCPUs an already
 182          * running guest has. So cap it up to X. */
 183         if (subtract)
 184                 nr_cpu_ids = nr_cpu_ids - subtract;
 185 #endif
 186
 187 }
 188
 189 static void __init xen_pv_smp_prepare_boot_cpu(void)
 190 {
 191         BUG_ON(smp_processor_id() != 0);
 192         native_smp_prepare_boot_cpu();
 193
 194         if (!xen_feature(XENFEAT_writable_page_tables))
 195                 /* We've switched to the "real" per-cpu gdt, so make
 196                  * sure the old memory can be recycled. */
 197                 make_lowmem_page_readwrite(xen_initial_gdt);
 198
 199         xen_setup_vcpu_info_placement();
 200
 201         /*
 202          * The alternative logic (which patches the unlock/lock) runs before
 203          * the smp bootup up code is activated. Hence we need to set this up
 204          * the core kernel is being patched. Otherwise we will have only
 205          * modules patched but not core code.
 206          */
 207         xen_init_spinlocks();
 208 }
 209
 210 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 211 {
 212         unsigned cpu;
 213         unsigned int i;
 214
 215         if (skip_ioapic_setup) {
 216                 char *m = (max_cpus == 0) ?
 217                         "The nosmp parameter is incompatible with Xen; " \
 218                         "use Xen dom0_max_vcpus=1 parameter" :
 219                         "The noapic parameter is incompatible with Xen";
 220
 221                 xen_raw_printk(m);
 222                 panic(m);
 223         }
 224         xen_init_lock_cpu(0);
 225
 226         smp_store_boot_cpu_info();
 227         cpu_data(0).x86_max_cores = 1;
 228
 229         for_each_possible_cpu(i) {
 230                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 231                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 232                 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
 233                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 234         }
 235         set_cpu_sibling_map(0);
 236
 237         speculative_store_bypass_ht_init();
 238
 239         xen_pmu_init(0);
 240
 241         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 242                 BUG();
 243
 244         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 245                 panic("could not allocate xen_cpu_initialized_map\n");
 246
 247         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 248
 249         /* Restrict the possible_map according to max_cpus. */
 250         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 251                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 252                         continue;
 253                 set_cpu_possible(cpu, false);
 254         }
 255
 256         for_each_possible_cpu(cpu)
 257                 set_cpu_present(cpu, true);
 258 }
 259
 260 static int
 261 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 262 {
 263         struct vcpu_guest_context *ctxt;
 264         struct desc_struct *gdt;
 265         unsigned long gdt_mfn;
 266
 267         /* used to tell cpu_init() that it can proceed with initialization */
 268         cpumask_set_cpu(cpu, cpu_callout_mask);
 269         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 270                 return 0;
 271
 272         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 273         if (ctxt == NULL)
 274                 return -ENOMEM;
 275
 276         gdt = get_cpu_gdt_rw(cpu);
 277
 278         /*
 279          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 280          * pointing just below where pt_regs would be if it were a normal
 281          * kernel entry.
 282          */
 283         ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
 284         ctxt->flags = VGCF_IN_KERNEL;
 285         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 286         ctxt->user_regs.ds = __USER_DS;
 287         ctxt->user_regs.es = __USER_DS;
 288         ctxt->user_regs.ss = __KERNEL_DS;
 289         ctxt->user_regs.cs = __KERNEL_CS;
 290         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 291
 292         xen_copy_trap_info(ctxt->trap_ctxt);
 293
 294         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 295
 296         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 297         make_lowmem_page_readonly(gdt);
 298         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 299
 300         ctxt->gdt_frames[0] = gdt_mfn;
 301         ctxt->gdt_ents      = GDT_ENTRIES;
 302
 303         /*
 304          * Set SS:SP that Xen will use when entering guest kernel mode
 305          * from guest user mode.  Subsequent calls to load_sp0() can
 306          * change this value.
 307          */
 308         ctxt->kernel_ss = __KERNEL_DS;
 309         ctxt->kernel_sp = task_top_of_stack(idle);
 310
 311         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 312         ctxt->event_callback_eip    =
 313                 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
 314         ctxt->failsafe_callback_eip =
 315                 (unsigned long)xen_failsafe_callback;
 316         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 317
 318         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 319         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 320                 BUG();
 321
 322         kfree(ctxt);
 323         return 0;
 324 }
 325
 326 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 327 {
 328         int rc;
 329
 330         rc = common_cpu_up(cpu, idle);
 331         if (rc)
 332                 return rc;
 333
 334         xen_setup_runstate_info(cpu);
 335
 336         /*
 337          * PV VCPUs are always successfully taken down (see 'while' loop
 338          * in xen_cpu_die()), so -EBUSY is an error.
 339          */
 340         rc = cpu_check_up_prepare(cpu);
 341         if (rc)
 342                 return rc;
 343
 344         /* make sure interrupts start blocked */
 345         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 346
 347         rc = cpu_initialize_context(cpu, idle);
 348         if (rc)
 349                 return rc;
 350
 351         xen_pmu_init(cpu);
 352
 353         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 354         BUG_ON(rc);
 355
 356         while (cpu_report_state(cpu) != CPU_ONLINE)
 357                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 358
 359         return 0;
 360 }
 361
 362 #ifdef CONFIG_HOTPLUG_CPU
 363 static int xen_pv_cpu_disable(void)
 364 {
 365         unsigned int cpu = smp_processor_id();
 366         if (cpu == 0)
 367                 return -EBUSY;
 368
 369         cpu_disable_common();
 370
 371         load_cr3(swapper_pg_dir);
 372         return 0;
 373 }
 374
 375 static void xen_pv_cpu_die(unsigned int cpu)
 376 {
 377         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 378                                   xen_vcpu_nr(cpu), NULL)) {
 379                 __set_current_state(TASK_UNINTERRUPTIBLE);
 380                 schedule_timeout(HZ/10);
 381         }
 382
 383         if (common_cpu_die(cpu) == 0) {
 384                 xen_smp_intr_free(cpu);
 385                 xen_uninit_lock_cpu(cpu);
 386                 xen_teardown_timer(cpu);
 387                 xen_pmu_finish(cpu);
 388         }
 389 }
 390
 391 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 392 {
 393         play_dead_common();
 394         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 395         cpu_bringup();
 396         /*
 397          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 398          * clears certain data that the cpu_idle loop (which called us
 399          * and that we return from) expects. The only way to get that
 400          * data back is to call:
 401          */
 402         tick_nohz_idle_enter();
 403         tick_nohz_idle_stop_tick_protected();
 404
 405         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 406 }
 407
 408 #else /* !CONFIG_HOTPLUG_CPU */
 409 static int xen_pv_cpu_disable(void)
 410 {
 411         return -ENOSYS;
 412 }
 413
 414 static void xen_pv_cpu_die(unsigned int cpu)
 415 {
 416         BUG();
 417 }
 418
 419 static void xen_pv_play_dead(void)
 420 {
 421         BUG();
 422 }
 423
 424 #endif
 425 static void stop_self(void *v)
 426 {
 427         int cpu = smp_processor_id();
 428
 429         /* make sure we're not pinning something down */
 430         load_cr3(swapper_pg_dir);
 431         /* should set up a minimal gdt */
 432
 433         set_cpu_online(cpu, false);
 434
 435         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 436         BUG();
 437 }
 438
 439 static void xen_pv_stop_other_cpus(int wait)
 440 {
 441         smp_call_function(stop_self, NULL, wait);
 442 }
 443
 444 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 445 {
 446         irq_enter();
 447         irq_work_run();
 448         inc_irq_stat(apic_irq_work_irqs);
 449         irq_exit();
 450
 451         return IRQ_HANDLED;
 452 }
 453
 454 static const struct smp_ops xen_smp_ops __initconst = {
 455         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 456         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 457         .smp_cpus_done = xen_smp_cpus_done,
 458
 459         .cpu_up = xen_pv_cpu_up,
 460         .cpu_die = xen_pv_cpu_die,
 461         .cpu_disable = xen_pv_cpu_disable,
 462         .play_dead = xen_pv_play_dead,
 463
 464         .stop_other_cpus = xen_pv_stop_other_cpus,
 465         .smp_send_reschedule = xen_smp_send_reschedule,
 466
 467         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 468         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 469 };
 470
 471 void __init xen_smp_init(void)
 472 {
 473         smp_ops = xen_smp_ops;
 474
 475         /* Avoid searching for BIOS MP tables */
 476         x86_init.mpparse.find_smp_config = x86_init_noop;
 477         x86_init.mpparse.get_smp_config = _get_smp_config;
 478 }