arch/x86/xen/smp_pv.c

   1 /*
   2  * Xen SMP support
   3  *
   4  * This file implements the Xen versions of smp_ops.  SMP under Xen is
   5  * very straightforward.  Bringing a CPU up is simply a matter of
   6  * loading its initial context and setting it running.
   7  *
   8  * IPIs are handled through the Xen event mechanism.
   9  *
  10  * Because virtual CPUs can be scheduled onto any real CPU, there's no
  11  * useful topology information for the kernel to make use of.  As a
  12  * result, all CPUs are treated as if they're single-core and
  13  * single-threaded.
  14  */
  15 #include <linux/sched.h>
  16 #include <linux/err.h>
  17 #include <linux/slab.h>
  18 #include <linux/smp.h>
  19 #include <linux/irq_work.h>
  20 #include <linux/tick.h>
  21 #include <linux/nmi.h>
  22
  23 #include <asm/paravirt.h>
  24 #include <asm/desc.h>
  25 #include <asm/pgtable.h>
  26 #include <asm/cpu.h>
  27
  28 #include <xen/interface/xen.h>
  29 #include <xen/interface/vcpu.h>
  30 #include <xen/interface/xenpmu.h>
  31
  32 #include <asm/xen/interface.h>
  33 #include <asm/xen/hypercall.h>
  34
  35 #include <xen/xen.h>
  36 #include <xen/page.h>
  37 #include <xen/events.h>
  38
  39 #include <xen/hvc-console.h>
  40 #include "xen-ops.h"
  41 #include "mmu.h"
  42 #include "smp.h"
  43 #include "pmu.h"
  44
  45 cpumask_var_t xen_cpu_initialized_map;
  46
  47 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  48 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  49
  50 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  51
  52 static void cpu_bringup(void)
  53 {
  54         int cpu;
  55
  56         cpu_init();
  57         touch_softlockup_watchdog();
  58         preempt_disable();
  59
  60         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  61         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  62                 xen_enable_sysenter();
  63                 xen_enable_syscall();
  64         }
  65         cpu = smp_processor_id();
  66         smp_store_cpu_info(cpu);
  67         cpu_data(cpu).x86_max_cores = 1;
  68         set_cpu_sibling_map(cpu);
  69
  70         xen_setup_cpu_clockevents();
  71
  72         notify_cpu_starting(cpu);
  73
  74         set_cpu_online(cpu, true);
  75
  76         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  77
  78         /* We can take interrupts now: we're officially "up". */
  79         local_irq_enable();
  80 }
  81
  82 asmlinkage __visible void cpu_bringup_and_idle(void)
  83 {
  84         cpu_bringup();
  85         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  86 }
  87
  88 void xen_smp_intr_free_pv(unsigned int cpu)
  89 {
  90         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
  91                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
  92                 per_cpu(xen_irq_work, cpu).irq = -1;
  93                 kfree(per_cpu(xen_irq_work, cpu).name);
  94                 per_cpu(xen_irq_work, cpu).name = NULL;
  95         }
  96
  97         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
  98                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
  99                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 100                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 101                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 102         }
 103 }
 104
 105 int xen_smp_intr_init_pv(unsigned int cpu)
 106 {
 107         int rc;
 108         char *callfunc_name, *pmu_name;
 109
 110         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 111         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 112                                     cpu,
 113                                     xen_irq_work_interrupt,
 114                                     IRQF_PERCPU|IRQF_NOBALANCING,
 115                                     callfunc_name,
 116                                     NULL);
 117         if (rc < 0)
 118                 goto fail;
 119         per_cpu(xen_irq_work, cpu).irq = rc;
 120         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 121
 122         if (is_xen_pmu(cpu)) {
 123                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 124                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 125                                              xen_pmu_irq_handler,
 126                                              IRQF_PERCPU|IRQF_NOBALANCING,
 127                                              pmu_name, NULL);
 128                 if (rc < 0)
 129                         goto fail;
 130                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 131                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 132         }
 133
 134         return 0;
 135
 136  fail:
 137         xen_smp_intr_free_pv(cpu);
 138         return rc;
 139 }
 140
 141 static void __init xen_fill_possible_map(void)
 142 {
 143         int i, rc;
 144
 145         if (xen_initial_domain())
 146                 return;
 147
 148         for (i = 0; i < nr_cpu_ids; i++) {
 149                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 150                 if (rc >= 0) {
 151                         num_processors++;
 152                         set_cpu_possible(i, true);
 153                 }
 154         }
 155 }
 156
 157 static void __init xen_filter_cpu_maps(void)
 158 {
 159         int i, rc;
 160         unsigned int subtract = 0;
 161
 162         if (!xen_initial_domain())
 163                 return;
 164
 165         num_processors = 0;
 166         disabled_cpus = 0;
 167         for (i = 0; i < nr_cpu_ids; i++) {
 168                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 169                 if (rc >= 0) {
 170                         num_processors++;
 171                         set_cpu_possible(i, true);
 172                 } else {
 173                         set_cpu_possible(i, false);
 174                         set_cpu_present(i, false);
 175                         subtract++;
 176                 }
 177         }
 178 #ifdef CONFIG_HOTPLUG_CPU
 179         /* This is akin to using 'nr_cpus' on the Linux command line.
 180          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 181          * have up to X, while nr_cpu_ids is greater than X. This
 182          * normally is not a problem, except when CPU hotplugging
 183          * is involved and then there might be more than X CPUs
 184          * in the guest - which will not work as there is no
 185          * hypercall to expand the max number of VCPUs an already
 186          * running guest has. So cap it up to X. */
 187         if (subtract)
 188                 nr_cpu_ids = nr_cpu_ids - subtract;
 189 #endif
 190
 191 }
 192
 193 static void __init xen_pv_smp_prepare_boot_cpu(void)
 194 {
 195         BUG_ON(smp_processor_id() != 0);
 196         native_smp_prepare_boot_cpu();
 197
 198         if (!xen_feature(XENFEAT_writable_page_tables))
 199                 /* We've switched to the "real" per-cpu gdt, so make
 200                  * sure the old memory can be recycled. */
 201                 make_lowmem_page_readwrite(xen_initial_gdt);
 202
 203 #ifdef CONFIG_X86_32
 204         /*
 205          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 206          * expects __USER_DS
 207          */
 208         loadsegment(ds, __USER_DS);
 209         loadsegment(es, __USER_DS);
 210 #endif
 211
 212         xen_filter_cpu_maps();
 213         xen_setup_vcpu_info_placement();
 214
 215         /*
 216          * The alternative logic (which patches the unlock/lock) runs before
 217          * the smp bootup up code is activated. Hence we need to set this up
 218          * the core kernel is being patched. Otherwise we will have only
 219          * modules patched but not core code.
 220          */
 221         xen_init_spinlocks();
 222 }
 223
 224 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
 225 {
 226         unsigned cpu;
 227         unsigned int i;
 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_store_boot_cpu_info();
 241         cpu_data(0).x86_max_cores = 1;
 242
 243         for_each_possible_cpu(i) {
 244                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 245                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 246                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 247         }
 248         set_cpu_sibling_map(0);
 249
 250         xen_pmu_init(0);
 251
 252         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 253                 BUG();
 254
 255         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 256                 panic("could not allocate xen_cpu_initialized_map\n");
 257
 258         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 259
 260         /* Restrict the possible_map according to max_cpus. */
 261         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 262                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 263                         continue;
 264                 set_cpu_possible(cpu, false);
 265         }
 266
 267         for_each_possible_cpu(cpu)
 268                 set_cpu_present(cpu, true);
 269 }
 270
 271 static int
 272 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 273 {
 274         struct vcpu_guest_context *ctxt;
 275         struct desc_struct *gdt;
 276         unsigned long gdt_mfn;
 277
 278         /* used to tell cpu_init() that it can proceed with initialization */
 279         cpumask_set_cpu(cpu, cpu_callout_mask);
 280         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 281                 return 0;
 282
 283         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 284         if (ctxt == NULL)
 285                 return -ENOMEM;
 286
 287         gdt = get_cpu_gdt_rw(cpu);
 288
 289 #ifdef CONFIG_X86_32
 290         ctxt->user_regs.fs = __KERNEL_PERCPU;
 291         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 292 #endif
 293         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 294
 295         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 296         ctxt->flags = VGCF_IN_KERNEL;
 297         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 298         ctxt->user_regs.ds = __USER_DS;
 299         ctxt->user_regs.es = __USER_DS;
 300         ctxt->user_regs.ss = __KERNEL_DS;
 301
 302         xen_copy_trap_info(ctxt->trap_ctxt);
 303
 304         ctxt->ldt_ents = 0;
 305
 306         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 307
 308         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 309         make_lowmem_page_readonly(gdt);
 310         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 311
 312         ctxt->gdt_frames[0] = gdt_mfn;
 313         ctxt->gdt_ents      = GDT_ENTRIES;
 314
 315         ctxt->kernel_ss = __KERNEL_DS;
 316         ctxt->kernel_sp = idle->thread.sp0;
 317
 318 #ifdef CONFIG_X86_32
 319         ctxt->event_callback_cs     = __KERNEL_CS;
 320         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 321 #else
 322         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 323 #endif
 324         ctxt->event_callback_eip    =
 325                 (unsigned long)xen_hypervisor_callback;
 326         ctxt->failsafe_callback_eip =
 327                 (unsigned long)xen_failsafe_callback;
 328         ctxt->user_regs.cs = __KERNEL_CS;
 329         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 330
 331         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
 332         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 333         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 334                 BUG();
 335
 336         kfree(ctxt);
 337         return 0;
 338 }
 339
 340 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 341 {
 342         int rc;
 343
 344         common_cpu_up(cpu, idle);
 345
 346         xen_setup_runstate_info(cpu);
 347
 348         /*
 349          * PV VCPUs are always successfully taken down (see 'while' loop
 350          * in xen_cpu_die()), so -EBUSY is an error.
 351          */
 352         rc = cpu_check_up_prepare(cpu);
 353         if (rc)
 354                 return rc;
 355
 356         /* make sure interrupts start blocked */
 357         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 358
 359         rc = cpu_initialize_context(cpu, idle);
 360         if (rc)
 361                 return rc;
 362
 363         xen_pmu_init(cpu);
 364
 365         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 366         BUG_ON(rc);
 367
 368         while (cpu_report_state(cpu) != CPU_ONLINE)
 369                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 370
 371         return 0;
 372 }
 373
 374 static void xen_pv_smp_cpus_done(unsigned int max_cpus)
 375 {
 376 }
 377
 378 #ifdef CONFIG_HOTPLUG_CPU
 379 static int xen_pv_cpu_disable(void)
 380 {
 381         unsigned int cpu = smp_processor_id();
 382         if (cpu == 0)
 383                 return -EBUSY;
 384
 385         cpu_disable_common();
 386
 387         load_cr3(swapper_pg_dir);
 388         return 0;
 389 }
 390
 391 static void xen_pv_cpu_die(unsigned int cpu)
 392 {
 393         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 394                                   xen_vcpu_nr(cpu), NULL)) {
 395                 __set_current_state(TASK_UNINTERRUPTIBLE);
 396                 schedule_timeout(HZ/10);
 397         }
 398
 399         if (common_cpu_die(cpu) == 0) {
 400                 xen_smp_intr_free(cpu);
 401                 xen_uninit_lock_cpu(cpu);
 402                 xen_teardown_timer(cpu);
 403                 xen_pmu_finish(cpu);
 404         }
 405 }
 406
 407 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 408 {
 409         play_dead_common();
 410         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 411         cpu_bringup();
 412         /*
 413          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 414          * clears certain data that the cpu_idle loop (which called us
 415          * and that we return from) expects. The only way to get that
 416          * data back is to call:
 417          */
 418         tick_nohz_idle_enter();
 419
 420         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 421 }
 422
 423 #else /* !CONFIG_HOTPLUG_CPU */
 424 static int xen_pv_cpu_disable(void)
 425 {
 426         return -ENOSYS;
 427 }
 428
 429 static void xen_pv_cpu_die(unsigned int cpu)
 430 {
 431         BUG();
 432 }
 433
 434 static void xen_pv_play_dead(void)
 435 {
 436         BUG();
 437 }
 438
 439 #endif
 440 static void stop_self(void *v)
 441 {
 442         int cpu = smp_processor_id();
 443
 444         /* make sure we're not pinning something down */
 445         load_cr3(swapper_pg_dir);
 446         /* should set up a minimal gdt */
 447
 448         set_cpu_online(cpu, false);
 449
 450         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 451         BUG();
 452 }
 453
 454 static void xen_pv_stop_other_cpus(int wait)
 455 {
 456         smp_call_function(stop_self, NULL, wait);
 457 }
 458
 459 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 460 {
 461         irq_enter();
 462         irq_work_run();
 463         inc_irq_stat(apic_irq_work_irqs);
 464         irq_exit();
 465
 466         return IRQ_HANDLED;
 467 }
 468
 469 static const struct smp_ops xen_smp_ops __initconst = {
 470         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 471         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 472         .smp_cpus_done = xen_pv_smp_cpus_done,
 473
 474         .cpu_up = xen_pv_cpu_up,
 475         .cpu_die = xen_pv_cpu_die,
 476         .cpu_disable = xen_pv_cpu_disable,
 477         .play_dead = xen_pv_play_dead,
 478
 479         .stop_other_cpus = xen_pv_stop_other_cpus,
 480         .smp_send_reschedule = xen_smp_send_reschedule,
 481
 482         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 483         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 484 };
 485
 486 void __init xen_smp_init(void)
 487 {
 488         smp_ops = xen_smp_ops;
 489         xen_fill_possible_map();
 490 }