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         preempt_disable();
  70
  71         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  72         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  73                 xen_enable_sysenter();
  74                 xen_enable_syscall();
  75         }
  76         cpu = smp_processor_id();
  77         smp_store_cpu_info(cpu);
  78         cpu_data(cpu).x86_max_cores = 1;
  79         set_cpu_sibling_map(cpu);
  80
  81         speculative_store_bypass_ht_init();
  82
  83         xen_setup_cpu_clockevents();
  84
  85         notify_cpu_starting(cpu);
  86
  87         set_cpu_online(cpu, true);
  88
  89         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  90
  91         /* We can take interrupts now: we're officially "up". */
  92         local_irq_enable();
  93 }
  94
  95 asmlinkage __visible void cpu_bringup_and_idle(void)
  96 {
  97         cpu_bringup();
  98         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  99 }
 100
 101 void xen_smp_intr_free_pv(unsigned int cpu)
 102 {
 103         kfree(per_cpu(xen_irq_work, cpu).name);
 104         per_cpu(xen_irq_work, cpu).name = NULL;
 105         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
 106                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 107                 per_cpu(xen_irq_work, cpu).irq = -1;
 108         }
 109
 110         kfree(per_cpu(xen_pmu_irq, cpu).name);
 111         per_cpu(xen_pmu_irq, cpu).name = NULL;
 112         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 113                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 114                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 115         }
 116 }
 117
 118 int xen_smp_intr_init_pv(unsigned int cpu)
 119 {
 120         int rc;
 121         char *callfunc_name, *pmu_name;
 122
 123         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 124         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 125         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 126                                     cpu,
 127                                     xen_irq_work_interrupt,
 128                                     IRQF_PERCPU|IRQF_NOBALANCING,
 129                                     callfunc_name,
 130                                     NULL);
 131         if (rc < 0)
 132                 goto fail;
 133         per_cpu(xen_irq_work, cpu).irq = rc;
 134
 135         if (is_xen_pmu) {
 136                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 137                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 138                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 139                                              xen_pmu_irq_handler,
 140                                              IRQF_PERCPU|IRQF_NOBALANCING,
 141                                              pmu_name, NULL);
 142                 if (rc < 0)
 143                         goto fail;
 144                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 145         }
 146
 147         return 0;
 148
 149  fail:
 150         xen_smp_intr_free_pv(cpu);
 151         return rc;
 152 }
 153
 154 static void __init _get_smp_config(unsigned int early)
 155 {
 156         int i, rc;
 157         unsigned int subtract = 0;
 158
 159         if (early)
 160                 return;
 161
 162         num_processors = 0;
 163         disabled_cpus = 0;
 164         for (i = 0; i < nr_cpu_ids; i++) {
 165                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 166                 if (rc >= 0) {
 167                         num_processors++;
 168                         set_cpu_possible(i, true);
 169                 } else {
 170                         set_cpu_possible(i, false);
 171                         set_cpu_present(i, false);
 172                         subtract++;
 173                 }
 174         }
 175 #ifdef CONFIG_HOTPLUG_CPU
 176         /* This is akin to using 'nr_cpus' on the Linux command line.
 177          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 178          * have up to X, while nr_cpu_ids is greater than X. This
 179          * normally is not a problem, except when CPU hotplugging
 180          * is involved and then there might be more than X CPUs
 181          * in the guest - which will not work as there is no
 182          * hypercall to expand the max number of VCPUs an already
 183          * running guest has. So cap it up to X. */
 184         if (subtract)
 185                 nr_cpu_ids = nr_cpu_ids - subtract;
 186 #endif
 187
 188 }
 189
 190 static void __init xen_pv_smp_prepare_boot_cpu(void)
 191 {
 192         BUG_ON(smp_processor_id() != 0);
 193         native_smp_prepare_boot_cpu();
 194
 195         if (!xen_feature(XENFEAT_writable_page_tables))
 196                 /* We've switched to the "real" per-cpu gdt, so make
 197                  * sure the old memory can be recycled. */
 198                 make_lowmem_page_readwrite(xen_initial_gdt);
 199
 200         xen_setup_vcpu_info_placement();
 201
 202         /*
 203          * The alternative logic (which patches the unlock/lock) runs before
 204          * the smp bootup up code is activated. Hence we need to set this up
 205          * the core kernel is being patched. Otherwise we will have only
 206          * modules patched but not core code.
 207          */
 208         xen_init_spinlocks();
 209 }
 210
 211 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 212 {
 213         unsigned cpu;
 214         unsigned int i;
 215
 216         if (skip_ioapic_setup) {
 217                 char *m = (max_cpus == 0) ?
 218                         "The nosmp parameter is incompatible with Xen; " \
 219                         "use Xen dom0_max_vcpus=1 parameter" :
 220                         "The noapic parameter is incompatible with Xen";
 221
 222                 xen_raw_printk(m);
 223                 panic(m);
 224         }
 225         xen_init_lock_cpu(0);
 226
 227         smp_store_boot_cpu_info();
 228         cpu_data(0).x86_max_cores = 1;
 229
 230         for_each_possible_cpu(i) {
 231                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 232                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 233                 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
 234                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 235         }
 236         set_cpu_sibling_map(0);
 237
 238         speculative_store_bypass_ht_init();
 239
 240         xen_pmu_init(0);
 241
 242         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 243                 BUG();
 244
 245         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 246                 panic("could not allocate xen_cpu_initialized_map\n");
 247
 248         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 249
 250         /* Restrict the possible_map according to max_cpus. */
 251         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 252                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 253                         continue;
 254                 set_cpu_possible(cpu, false);
 255         }
 256
 257         for_each_possible_cpu(cpu)
 258                 set_cpu_present(cpu, true);
 259 }
 260
 261 static int
 262 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 263 {
 264         struct vcpu_guest_context *ctxt;
 265         struct desc_struct *gdt;
 266         unsigned long gdt_mfn;
 267
 268         /* used to tell cpu_init() that it can proceed with initialization */
 269         cpumask_set_cpu(cpu, cpu_callout_mask);
 270         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 271                 return 0;
 272
 273         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 274         if (ctxt == NULL)
 275                 return -ENOMEM;
 276
 277         gdt = get_cpu_gdt_rw(cpu);
 278
 279         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 280
 281         /*
 282          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 283          * pointing just below where pt_regs would be if it were a normal
 284          * kernel entry.
 285          */
 286         ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
 287         ctxt->flags = VGCF_IN_KERNEL;
 288         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 289         ctxt->user_regs.ds = __USER_DS;
 290         ctxt->user_regs.es = __USER_DS;
 291         ctxt->user_regs.ss = __KERNEL_DS;
 292         ctxt->user_regs.cs = __KERNEL_CS;
 293         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 294
 295         xen_copy_trap_info(ctxt->trap_ctxt);
 296
 297         ctxt->ldt_ents = 0;
 298
 299         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 300
 301         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 302         make_lowmem_page_readonly(gdt);
 303         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 304
 305         ctxt->gdt_frames[0] = gdt_mfn;
 306         ctxt->gdt_ents      = GDT_ENTRIES;
 307
 308         /*
 309          * Set SS:SP that Xen will use when entering guest kernel mode
 310          * from guest user mode.  Subsequent calls to load_sp0() can
 311          * change this value.
 312          */
 313         ctxt->kernel_ss = __KERNEL_DS;
 314         ctxt->kernel_sp = task_top_of_stack(idle);
 315
 316         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 317         ctxt->event_callback_eip    =
 318                 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
 319         ctxt->failsafe_callback_eip =
 320                 (unsigned long)xen_failsafe_callback;
 321         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 322
 323         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 324         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 325                 BUG();
 326
 327         kfree(ctxt);
 328         return 0;
 329 }
 330
 331 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 332 {
 333         int rc;
 334
 335         rc = common_cpu_up(cpu, idle);
 336         if (rc)
 337                 return rc;
 338
 339         xen_setup_runstate_info(cpu);
 340
 341         /*
 342          * PV VCPUs are always successfully taken down (see 'while' loop
 343          * in xen_cpu_die()), so -EBUSY is an error.
 344          */
 345         rc = cpu_check_up_prepare(cpu);
 346         if (rc)
 347                 return rc;
 348
 349         /* make sure interrupts start blocked */
 350         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 351
 352         rc = cpu_initialize_context(cpu, idle);
 353         if (rc)
 354                 return rc;
 355
 356         xen_pmu_init(cpu);
 357
 358         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 359         BUG_ON(rc);
 360
 361         while (cpu_report_state(cpu) != CPU_ONLINE)
 362                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 363
 364         return 0;
 365 }
 366
 367 #ifdef CONFIG_HOTPLUG_CPU
 368 static int xen_pv_cpu_disable(void)
 369 {
 370         unsigned int cpu = smp_processor_id();
 371         if (cpu == 0)
 372                 return -EBUSY;
 373
 374         cpu_disable_common();
 375
 376         load_cr3(swapper_pg_dir);
 377         return 0;
 378 }
 379
 380 static void xen_pv_cpu_die(unsigned int cpu)
 381 {
 382         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 383                                   xen_vcpu_nr(cpu), NULL)) {
 384                 __set_current_state(TASK_UNINTERRUPTIBLE);
 385                 schedule_timeout(HZ/10);
 386         }
 387
 388         if (common_cpu_die(cpu) == 0) {
 389                 xen_smp_intr_free(cpu);
 390                 xen_uninit_lock_cpu(cpu);
 391                 xen_teardown_timer(cpu);
 392                 xen_pmu_finish(cpu);
 393         }
 394 }
 395
 396 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 397 {
 398         play_dead_common();
 399         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 400         cpu_bringup();
 401         /*
 402          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 403          * clears certain data that the cpu_idle loop (which called us
 404          * and that we return from) expects. The only way to get that
 405          * data back is to call:
 406          */
 407         tick_nohz_idle_enter();
 408         tick_nohz_idle_stop_tick_protected();
 409
 410         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 411 }
 412
 413 #else /* !CONFIG_HOTPLUG_CPU */
 414 static int xen_pv_cpu_disable(void)
 415 {
 416         return -ENOSYS;
 417 }
 418
 419 static void xen_pv_cpu_die(unsigned int cpu)
 420 {
 421         BUG();
 422 }
 423
 424 static void xen_pv_play_dead(void)
 425 {
 426         BUG();
 427 }
 428
 429 #endif
 430 static void stop_self(void *v)
 431 {
 432         int cpu = smp_processor_id();
 433
 434         /* make sure we're not pinning something down */
 435         load_cr3(swapper_pg_dir);
 436         /* should set up a minimal gdt */
 437
 438         set_cpu_online(cpu, false);
 439
 440         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 441         BUG();
 442 }
 443
 444 static void xen_pv_stop_other_cpus(int wait)
 445 {
 446         smp_call_function(stop_self, NULL, wait);
 447 }
 448
 449 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 450 {
 451         irq_enter();
 452         irq_work_run();
 453         inc_irq_stat(apic_irq_work_irqs);
 454         irq_exit();
 455
 456         return IRQ_HANDLED;
 457 }
 458
 459 static const struct smp_ops xen_smp_ops __initconst = {
 460         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 461         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 462         .smp_cpus_done = xen_smp_cpus_done,
 463
 464         .cpu_up = xen_pv_cpu_up,
 465         .cpu_die = xen_pv_cpu_die,
 466         .cpu_disable = xen_pv_cpu_disable,
 467         .play_dead = xen_pv_play_dead,
 468
 469         .stop_other_cpus = xen_pv_stop_other_cpus,
 470         .smp_send_reschedule = xen_smp_send_reschedule,
 471
 472         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 473         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 474 };
 475
 476 void __init xen_smp_init(void)
 477 {
 478         smp_ops = xen_smp_ops;
 479
 480         /* Avoid searching for BIOS MP tables */
 481         x86_init.mpparse.find_smp_config = x86_init_noop;
 482         x86_init.mpparse.get_smp_config = _get_smp_config;
 483 }