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 #include <linux/cpuhotplug.h>
  23
  24 #include <asm/paravirt.h>
  25 #include <asm/desc.h>
  26 #include <asm/pgtable.h>
  27 #include <asm/cpu.h>
  28
  29 #include <xen/interface/xen.h>
  30 #include <xen/interface/vcpu.h>
  31 #include <xen/interface/xenpmu.h>
  32
  33 #include <asm/xen/interface.h>
  34 #include <asm/xen/hypercall.h>
  35
  36 #include <xen/xen.h>
  37 #include <xen/page.h>
  38 #include <xen/events.h>
  39
  40 #include <xen/hvc-console.h>
  41 #include "xen-ops.h"
  42 #include "mmu.h"
  43 #include "smp.h"
  44 #include "pmu.h"
  45
  46 cpumask_var_t xen_cpu_initialized_map;
  47
  48 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
  49 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
  50
  51 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
  52
  53 static void cpu_bringup(void)
  54 {
  55         int cpu;
  56
  57         cpu_init();
  58         touch_softlockup_watchdog();
  59         preempt_disable();
  60
  61         /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
  62         if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
  63                 xen_enable_sysenter();
  64                 xen_enable_syscall();
  65         }
  66         cpu = smp_processor_id();
  67         smp_store_cpu_info(cpu);
  68         cpu_data(cpu).x86_max_cores = 1;
  69         set_cpu_sibling_map(cpu);
  70
  71         xen_setup_cpu_clockevents();
  72
  73         notify_cpu_starting(cpu);
  74
  75         set_cpu_online(cpu, true);
  76
  77         cpu_set_state_online(cpu);  /* Implies full memory barrier. */
  78
  79         /* We can take interrupts now: we're officially "up". */
  80         local_irq_enable();
  81 }
  82
  83 asmlinkage __visible void cpu_bringup_and_idle(void)
  84 {
  85         cpu_bringup();
  86         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
  87 }
  88
  89 void xen_smp_intr_free_pv(unsigned int cpu)
  90 {
  91         if (per_cpu(xen_irq_work, cpu).irq >= 0) {
  92                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
  93                 per_cpu(xen_irq_work, cpu).irq = -1;
  94                 kfree(per_cpu(xen_irq_work, cpu).name);
  95                 per_cpu(xen_irq_work, cpu).name = NULL;
  96         }
  97
  98         if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
  99                 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
 100                 per_cpu(xen_pmu_irq, cpu).irq = -1;
 101                 kfree(per_cpu(xen_pmu_irq, cpu).name);
 102                 per_cpu(xen_pmu_irq, cpu).name = NULL;
 103         }
 104 }
 105
 106 int xen_smp_intr_init_pv(unsigned int cpu)
 107 {
 108         int rc;
 109         char *callfunc_name, *pmu_name;
 110
 111         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
 112         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
 113                                     cpu,
 114                                     xen_irq_work_interrupt,
 115                                     IRQF_PERCPU|IRQF_NOBALANCING,
 116                                     callfunc_name,
 117                                     NULL);
 118         if (rc < 0)
 119                 goto fail;
 120         per_cpu(xen_irq_work, cpu).irq = rc;
 121         per_cpu(xen_irq_work, cpu).name = callfunc_name;
 122
 123         if (is_xen_pmu(cpu)) {
 124                 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 125                 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 126                                              xen_pmu_irq_handler,
 127                                              IRQF_PERCPU|IRQF_NOBALANCING,
 128                                              pmu_name, NULL);
 129                 if (rc < 0)
 130                         goto fail;
 131                 per_cpu(xen_pmu_irq, cpu).irq = rc;
 132                 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
 133         }
 134
 135         return 0;
 136
 137  fail:
 138         xen_smp_intr_free_pv(cpu);
 139         return rc;
 140 }
 141
 142 static void __init xen_fill_possible_map(void)
 143 {
 144         int i, rc;
 145
 146         if (xen_initial_domain())
 147                 return;
 148
 149         for (i = 0; i < nr_cpu_ids; i++) {
 150                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 151                 if (rc >= 0) {
 152                         num_processors++;
 153                         set_cpu_possible(i, true);
 154                 }
 155         }
 156 }
 157
 158 static void __init xen_filter_cpu_maps(void)
 159 {
 160         int i, rc;
 161         unsigned int subtract = 0;
 162
 163         if (!xen_initial_domain())
 164                 return;
 165
 166         num_processors = 0;
 167         disabled_cpus = 0;
 168         for (i = 0; i < nr_cpu_ids; i++) {
 169                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 170                 if (rc >= 0) {
 171                         num_processors++;
 172                         set_cpu_possible(i, true);
 173                 } else {
 174                         set_cpu_possible(i, false);
 175                         set_cpu_present(i, false);
 176                         subtract++;
 177                 }
 178         }
 179 #ifdef CONFIG_HOTPLUG_CPU
 180         /* This is akin to using 'nr_cpus' on the Linux command line.
 181          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 182          * have up to X, while nr_cpu_ids is greater than X. This
 183          * normally is not a problem, except when CPU hotplugging
 184          * is involved and then there might be more than X CPUs
 185          * in the guest - which will not work as there is no
 186          * hypercall to expand the max number of VCPUs an already
 187          * running guest has. So cap it up to X. */
 188         if (subtract)
 189                 nr_cpu_ids = nr_cpu_ids - subtract;
 190 #endif
 191
 192 }
 193
 194 static void __init xen_pv_smp_prepare_boot_cpu(void)
 195 {
 196         BUG_ON(smp_processor_id() != 0);
 197         native_smp_prepare_boot_cpu();
 198
 199         if (!xen_feature(XENFEAT_writable_page_tables))
 200                 /* We've switched to the "real" per-cpu gdt, so make
 201                  * sure the old memory can be recycled. */
 202                 make_lowmem_page_readwrite(xen_initial_gdt);
 203
 204 #ifdef CONFIG_X86_32
 205         /*
 206          * Xen starts us with XEN_FLAT_RING1_DS, but linux code
 207          * expects __USER_DS
 208          */
 209         loadsegment(ds, __USER_DS);
 210         loadsegment(es, __USER_DS);
 211 #endif
 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         unsigned int i;
 229
 230         if (skip_ioapic_setup) {
 231                 char *m = (max_cpus == 0) ?
 232                         "The nosmp parameter is incompatible with Xen; " \
 233                         "use Xen dom0_max_vcpus=1 parameter" :
 234                         "The noapic parameter is incompatible with Xen";
 235
 236                 xen_raw_printk(m);
 237                 panic(m);
 238         }
 239         xen_init_lock_cpu(0);
 240
 241         smp_store_boot_cpu_info();
 242         cpu_data(0).x86_max_cores = 1;
 243
 244         for_each_possible_cpu(i) {
 245                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 246                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 247                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 248         }
 249         set_cpu_sibling_map(0);
 250
 251         xen_pmu_init(0);
 252
 253         if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
 254                 BUG();
 255
 256         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 257                 panic("could not allocate xen_cpu_initialized_map\n");
 258
 259         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 260
 261         /* Restrict the possible_map according to max_cpus. */
 262         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 263                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 264                         continue;
 265                 set_cpu_possible(cpu, false);
 266         }
 267
 268         for_each_possible_cpu(cpu)
 269                 set_cpu_present(cpu, true);
 270 }
 271
 272 static int
 273 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 274 {
 275         struct vcpu_guest_context *ctxt;
 276         struct desc_struct *gdt;
 277         unsigned long gdt_mfn;
 278
 279         /* used to tell cpu_init() that it can proceed with initialization */
 280         cpumask_set_cpu(cpu, cpu_callout_mask);
 281         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 282                 return 0;
 283
 284         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 285         if (ctxt == NULL)
 286                 return -ENOMEM;
 287
 288         gdt = get_cpu_gdt_rw(cpu);
 289
 290 #ifdef CONFIG_X86_32
 291         ctxt->user_regs.fs = __KERNEL_PERCPU;
 292         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 293 #endif
 294         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 295
 296         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 297         ctxt->flags = VGCF_IN_KERNEL;
 298         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 299         ctxt->user_regs.ds = __USER_DS;
 300         ctxt->user_regs.es = __USER_DS;
 301         ctxt->user_regs.ss = __KERNEL_DS;
 302
 303         xen_copy_trap_info(ctxt->trap_ctxt);
 304
 305         ctxt->ldt_ents = 0;
 306
 307         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 308
 309         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 310         make_lowmem_page_readonly(gdt);
 311         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 312
 313         ctxt->gdt_frames[0] = gdt_mfn;
 314         ctxt->gdt_ents      = GDT_ENTRIES;
 315
 316         ctxt->kernel_ss = __KERNEL_DS;
 317         ctxt->kernel_sp = idle->thread.sp0;
 318
 319 #ifdef CONFIG_X86_32
 320         ctxt->event_callback_cs     = __KERNEL_CS;
 321         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 322 #else
 323         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 324 #endif
 325         ctxt->event_callback_eip    =
 326                 (unsigned long)xen_hypervisor_callback;
 327         ctxt->failsafe_callback_eip =
 328                 (unsigned long)xen_failsafe_callback;
 329         ctxt->user_regs.cs = __KERNEL_CS;
 330         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 331
 332         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
 333         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
 334         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
 335                 BUG();
 336
 337         kfree(ctxt);
 338         return 0;
 339 }
 340
 341 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 342 {
 343         int rc;
 344
 345         common_cpu_up(cpu, idle);
 346
 347         xen_setup_runstate_info(cpu);
 348
 349         /*
 350          * PV VCPUs are always successfully taken down (see 'while' loop
 351          * in xen_cpu_die()), so -EBUSY is an error.
 352          */
 353         rc = cpu_check_up_prepare(cpu);
 354         if (rc)
 355                 return rc;
 356
 357         /* make sure interrupts start blocked */
 358         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 359
 360         rc = cpu_initialize_context(cpu, idle);
 361         if (rc)
 362                 return rc;
 363
 364         xen_pmu_init(cpu);
 365
 366         rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
 367         BUG_ON(rc);
 368
 369         while (cpu_report_state(cpu) != CPU_ONLINE)
 370                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 371
 372         return 0;
 373 }
 374
 375 #ifdef CONFIG_HOTPLUG_CPU
 376 static int xen_pv_cpu_disable(void)
 377 {
 378         unsigned int cpu = smp_processor_id();
 379         if (cpu == 0)
 380                 return -EBUSY;
 381
 382         cpu_disable_common();
 383
 384         load_cr3(swapper_pg_dir);
 385         return 0;
 386 }
 387
 388 static void xen_pv_cpu_die(unsigned int cpu)
 389 {
 390         while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
 391                                   xen_vcpu_nr(cpu), NULL)) {
 392                 __set_current_state(TASK_UNINTERRUPTIBLE);
 393                 schedule_timeout(HZ/10);
 394         }
 395
 396         if (common_cpu_die(cpu) == 0) {
 397                 xen_smp_intr_free(cpu);
 398                 xen_uninit_lock_cpu(cpu);
 399                 xen_teardown_timer(cpu);
 400                 xen_pmu_finish(cpu);
 401         }
 402 }
 403
 404 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
 405 {
 406         play_dead_common();
 407         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
 408         cpu_bringup();
 409         /*
 410          * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
 411          * clears certain data that the cpu_idle loop (which called us
 412          * and that we return from) expects. The only way to get that
 413          * data back is to call:
 414          */
 415         tick_nohz_idle_enter();
 416
 417         cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
 418 }
 419
 420 #else /* !CONFIG_HOTPLUG_CPU */
 421 static int xen_pv_cpu_disable(void)
 422 {
 423         return -ENOSYS;
 424 }
 425
 426 static void xen_pv_cpu_die(unsigned int cpu)
 427 {
 428         BUG();
 429 }
 430
 431 static void xen_pv_play_dead(void)
 432 {
 433         BUG();
 434 }
 435
 436 #endif
 437 static void stop_self(void *v)
 438 {
 439         int cpu = smp_processor_id();
 440
 441         /* make sure we're not pinning something down */
 442         load_cr3(swapper_pg_dir);
 443         /* should set up a minimal gdt */
 444
 445         set_cpu_online(cpu, false);
 446
 447         HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
 448         BUG();
 449 }
 450
 451 static void xen_pv_stop_other_cpus(int wait)
 452 {
 453         smp_call_function(stop_self, NULL, wait);
 454 }
 455
 456 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 457 {
 458         irq_enter();
 459         irq_work_run();
 460         inc_irq_stat(apic_irq_work_irqs);
 461         irq_exit();
 462
 463         return IRQ_HANDLED;
 464 }
 465
 466 static const struct smp_ops xen_smp_ops __initconst = {
 467         .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
 468         .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
 469         .smp_cpus_done = xen_smp_cpus_done,
 470
 471         .cpu_up = xen_pv_cpu_up,
 472         .cpu_die = xen_pv_cpu_die,
 473         .cpu_disable = xen_pv_cpu_disable,
 474         .play_dead = xen_pv_play_dead,
 475
 476         .stop_other_cpus = xen_pv_stop_other_cpus,
 477         .smp_send_reschedule = xen_smp_send_reschedule,
 478
 479         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 480         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 481 };
 482
 483 void __init xen_smp_init(void)
 484 {
 485         smp_ops = xen_smp_ops;
 486         xen_fill_possible_map();
 487 }