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
  34 #include <xen/interface/xen.h>
  35 #include <xen/interface/vcpu.h>
  36 #include <xen/interface/xenpmu.h>
  37
  38 #include <asm/spec-ctrl.h>
  39 #include <asm/xen/interface.h>
  40 #include <asm/xen/hypercall.h>
  41
  42 #include <xen/xen.h>
  43 #include <xen/page.h>
  44 #include <xen/events.h>
  45
  46 #include <xen/hvc-console.h>
  47 #include "xen-ops.h"
  48 #include "mmu.h"
  49 #include "smp.h"
  50 #include "pmu.h"
  51
  52 cpumask_var_t xen_cpu_initialized_map;
  53
  54 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  55 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  56
  57 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  58 void asm_cpu_bringup_and_idle(void);
  59
  60 static void cpu_bringup(void)
  61 {
  62         int cpu;
  63
  64         cr4_init();
  65         cpu_init();
  66         touch_softlockup_watchdog();
  67
  68         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  69         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  70                 xen_enable_sysenter();
  71                 xen_enable_syscall();
  72         }
  73         cpu = smp_processor_id();
  74         smp_store_cpu_info(cpu);
  75         cpu_data(cpu).x86_max_cores = 1;
  76         set_cpu_sibling_map(cpu);
  77
  78         speculative_store_bypass_ht_init();
  79
  80         xen_setup_cpu_clockevents();
  81
  82         notify_cpu_starting(cpu);
  83
  84         set_cpu_online(cpu, true);
  85
  86         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  87
  88         /* We can take interrupts now: we're officially "up". */
  89         local_irq_enable();
  90 }
  91
  92 asmlinkage __visible void cpu_bringup_and_idle(void)
  93 {
  94         cpu_bringup();
  95         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  96 }
  97
  98 void xen_smp_intr_free_pv(unsigned int cpu)
  99 {
 100         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
 101                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
 102                 per_cpu(xen_irq_work, cpu).irq = -1;
 103                 kfree(per_cpu(xen_irq_work, cpu).name);
 104                 per_cpu(xen_irq_work, cpu).name = NULL;
 105         }
 106
 107         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
 108                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 109                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 110                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 111                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 112         }
 113 }
 114
 115 int xen_smp_intr_init_pv(unsigned int cpu)
 116 {
 117         int rc;
 118         char *callfunc_name, *pmu_name;
 119
 120         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 121         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 122                                     cpu,
 123                                     xen_irq_work_interrupt,
 124                                     IRQF_PERCPU|IRQF_NOBALANCING,
 125                                     callfunc_name,
 126                                     NULL);
 127         if (rc < 0)
 128                 goto fail;
 129         per_cpu(xen_irq_work, cpu).irq = rc;
 130         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 131
 132         if (is_xen_pmu(cpu)) {
 133                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 134                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 135                                              xen_pmu_irq_handler,
 136                                              IRQF_PERCPU|IRQF_NOBALANCING,
 137                                              pmu_name, NULL);
 138                 if (rc < 0)
 139                         goto fail;
 140                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 141                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 142         }
 143
 144         return 0;
 145
 146  fail:
 147         xen_smp_intr_free_pv(cpu);
 148         return rc;
 149 }
 150
 151 static void __init xen_fill_possible_map(void)
 152 {
 153         int i, rc;
 154
 155         if (xen_initial_domain())
 156                 return;
 157
 158         for (i = 0; i < nr_cpu_ids; i++) {
 159                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 160                 if (rc >= 0) {
 161                         num_processors++;
 162                         set_cpu_possible(i, true);
 163                 }
 164         }
 165 }
 166
 167 static void __init xen_filter_cpu_maps(void)
 168 {
 169         int i, rc;
 170         unsigned int subtract = 0;
 171
 172         if (!xen_initial_domain())
 173                 return;
 174
 175         num_processors = 0;
 176         disabled_cpus = 0;
 177         for (i = 0; i < nr_cpu_ids; i++) {
 178                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 179                 if (rc >= 0) {
 180                         num_processors++;
 181                         set_cpu_possible(i, true);
 182                 } else {
 183                         set_cpu_possible(i, false);
 184                         set_cpu_present(i, false);
 185                         subtract++;
 186                 }
 187         }
 188 #ifdef CONFIG_HOTPLUG_CPU
 189         /* This is akin to using 'nr_cpus' on the Linux command line.
 190          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 191          * have up to X, while nr_cpu_ids is greater than X. This
 192          * normally is not a problem, except when CPU hotplugging
 193          * is involved and then there might be more than X CPUs
 194          * in the guest - which will not work as there is no
 195          * hypercall to expand the max number of VCPUs an already
 196          * running guest has. So cap it up to X. */
 197         if (subtract)
 198                 nr_cpu_ids = nr_cpu_ids - subtract;
 199 #endif
 200
 201 }
 202
 203 static void __init xen_pv_smp_prepare_boot_cpu(void)
 204 {
 205         BUG_ON(smp_processor_id() != 0);
 206         native_smp_prepare_boot_cpu();
 207
 208         if (!xen_feature(XENFEAT_writable_page_tables))
 209                 /* We've switched to the "real" per-cpu gdt, so make
 210                  * sure the old memory can be recycled. */
 211                 make_lowmem_page_readwrite(xen_initial_gdt);
 212
 213         xen_filter_cpu_maps();
 214         xen_setup_vcpu_info_placement();
 215
 216         /*
 217          * The alternative logic (which patches the unlock/lock) runs before
 218          * the smp bootup up code is activated. Hence we need to set this up
 219          * the core kernel is being patched. Otherwise we will have only
 220          * modules patched but not core code.
 221          */
 222         xen_init_spinlocks();
 223 }
 224
 225 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 226 {
 227         unsigned cpu;
 228
 229         if (skip_ioapic_setup) {
 230                 char *m = (max_cpus == 0) ?
 231                         "The nosmp parameter is incompatible with Xen; " \
 232                         "use Xen dom0_max_vcpus=1 parameter" :
 233                         "The noapic parameter is incompatible with Xen";
 234
 235                 xen_raw_printk(m);
 236                 panic(m);
 237         }
 238         xen_init_lock_cpu(0);
 239
 240         smp_prepare_cpus_common();
 241
 242         cpu_data(0).x86_max_cores = 1;
 243
 244         speculative_store_bypass_ht_init();
 245
 246         xen_pmu_init(0);
 247
 248         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 249                 BUG();
 250
 251         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 252                 panic("could not allocate xen_cpu_initialized_map\n");
 253
 254         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 255
 256         /* Restrict the possible_map according to max_cpus. */
 257         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 258                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 259                         continue;
 260                 set_cpu_possible(cpu, false);
 261         }
 262
 263         for_each_possible_cpu(cpu)
 264                 set_cpu_present(cpu, true);
 265 }
 266
 267 static int
 268 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 269 {
 270         struct vcpu_guest_context *ctxt;
 271         struct desc_struct *gdt;
 272         unsigned long gdt_mfn;
 273
 274         /* used to tell cpu_init() that it can proceed with initialization */
 275         cpumask_set_cpu(cpu, cpu_callout_mask);
 276         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 277                 return 0;
 278
 279         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 280         if (ctxt == NULL)
 281                 return -ENOMEM;
 282
 283         gdt = get_cpu_gdt_rw(cpu);
 284
 285         /*
 286          * Bring up the CPU in cpu_bringup_and_idle() with the stack
 287          * pointing just below where pt_regs would be if it were a normal
 288          * kernel entry.
 289          */
 290         ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
 291         ctxt->flags = VGCF_IN_KERNEL;
 292         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 293         ctxt->user_regs.ds = __USER_DS;
 294         ctxt->user_regs.es = __USER_DS;
 295         ctxt->user_regs.ss = __KERNEL_DS;
 296         ctxt->user_regs.cs = __KERNEL_CS;
 297         ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 298
 299         xen_copy_trap_info(ctxt->trap_ctxt);
 300
 301         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 302
 303         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 304         make_lowmem_page_readonly(gdt);
 305         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 306
 307         ctxt->gdt_frames[0] = gdt_mfn;
 308         ctxt->gdt_ents      = GDT_ENTRIES;
 309
 310         /*
 311          * Set SS:SP that Xen will use when entering guest kernel mode
 312          * from guest user mode.  Subsequent calls to load_sp0() can
 313          * change this value.
 314          */
 315         ctxt->kernel_ss = __KERNEL_DS;
 316         ctxt->kernel_sp = task_top_of_stack(idle);
 317
 318         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 319         ctxt->event_callback_eip    =
 320                 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
 321         ctxt->failsafe_callback_eip =
 322                 (unsigned long)xen_failsafe_callback;
 323         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 324
 325         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 326         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 327                 BUG();
 328
 329         kfree(ctxt);
 330         return 0;
 331 }
 332
 333 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 334 {
 335         int rc;
 336
 337         rc = common_cpu_up(cpu, idle);
 338         if (rc)
 339                 return rc;
 340
 341         xen_setup_runstate_info(cpu);
 342
 343         /*
 344          * PV VCPUs are always successfully taken down (see 'while' loop
 345          * in xen_cpu_die()), so -EBUSY is an error.
 346          */
 347         rc = cpu_check_up_prepare(cpu);
 348         if (rc)
 349                 return rc;
 350
 351         /* make sure interrupts start blocked */
 352         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 353
 354         rc = cpu_initialize_context(cpu, idle);
 355         if (rc)
 356                 return rc;
 357
 358         xen_pmu_init(cpu);
 359
 360         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 361         BUG_ON(rc);
 362
 363         while (cpu_report_state(cpu) != CPU_ONLINE)
 364                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 365
 366         return 0;
 367 }
 368
 369 #ifdef CONFIG_HOTPLUG_CPU
 370 static int xen_pv_cpu_disable(void)
 371 {
 372         unsigned int cpu = smp_processor_id();
 373         if (cpu == 0)
 374                 return -EBUSY;
 375
 376         cpu_disable_common();
 377
 378         load_cr3(swapper_pg_dir);
 379         return 0;
 380 }
 381
 382 static void xen_pv_cpu_die(unsigned int cpu)
 383 {
 384         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 385                                   xen_vcpu_nr(cpu), NULL)) {
 386                 __set_current_state(TASK_UNINTERRUPTIBLE);
 387                 schedule_timeout(HZ/10);
 388         }
 389
 390         if (common_cpu_die(cpu) == 0) {
 391                 xen_smp_intr_free(cpu);
 392                 xen_uninit_lock_cpu(cpu);
 393                 xen_teardown_timer(cpu);
 394                 xen_pmu_finish(cpu);
 395         }
 396 }
 397
 398 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 399 {
 400         play_dead_common();
 401         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 402         cpu_bringup();
 403         /*
 404          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 405          * clears certain data that the cpu_idle loop (which called us
 406          * and that we return from) expects. The only way to get that
 407          * data back is to call:
 408          */
 409         tick_nohz_idle_enter();
 410         tick_nohz_idle_stop_tick_protected();
 411
 412         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 413 }
 414
 415 #else /* !CONFIG_HOTPLUG_CPU */
 416 static int xen_pv_cpu_disable(void)
 417 {
 418         return -ENOSYS;
 419 }
 420
 421 static void xen_pv_cpu_die(unsigned int cpu)
 422 {
 423         BUG();
 424 }
 425
 426 static void xen_pv_play_dead(void)
 427 {
 428         BUG();
 429 }
 430
 431 #endif
 432 static void stop_self(void *v)
 433 {
 434         int cpu = smp_processor_id();
 435
 436         /* make sure we're not pinning something down */
 437         load_cr3(swapper_pg_dir);
 438         /* should set up a minimal gdt */
 439
 440         set_cpu_online(cpu, false);
 441
 442         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 443         BUG();
 444 }
 445
 446 static void xen_pv_stop_other_cpus(int wait)
 447 {
 448         smp_call_function(stop_self, NULL, wait);
 449 }
 450
 451 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 452 {
 453         irq_work_run();
 454         inc_irq_stat(apic_irq_work_irqs);
 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         xen_fill_possible_map();
 480 }