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   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
  20 #include <asm/paravirt.h>
  21 #include <asm/desc.h>
  22 #include <asm/pgtable.h>
  23 #include <asm/cpu.h>
  24
  25 #include <xen/interface/xen.h>
  26 #include <xen/interface/vcpu.h>
  27
  28 #include <asm/xen/interface.h>
  29 #include <asm/xen/hypercall.h>
  30
  31 #include <xen/page.h>
  32 #include <xen/events.h>
  33
  34 #include "xen-ops.h"
  35 #include "mmu.h"
  36
  37 cpumask_var_t xen_cpu_initialized_map;
  38
  39 static DEFINE_PER_CPU(int, xen_resched_irq);
  40 static DEFINE_PER_CPU(int, xen_callfunc_irq);
  41 static DEFINE_PER_CPU(int, xen_callfuncsingle_irq);
  42 static DEFINE_PER_CPU(int, xen_debug_irq) = -1;
  43
  44 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
  45 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
  46
  47 /*
  48  * Reschedule call back. Nothing to do,
  49  * all the work is done automatically when
  50  * we return from the interrupt.
  51  */
  52 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
  53 {
  54         inc_irq_stat(irq_resched_count);
  55
  56         return IRQ_HANDLED;
  57 }
  58
  59 static __cpuinit void cpu_bringup(void)
  60 {
  61         int cpu = smp_processor_id();
  62
  63         cpu_init();
  64         touch_softlockup_watchdog();
  65         preempt_disable();
  66
  67         xen_enable_sysenter();
  68         xen_enable_syscall();
  69
  70         cpu = smp_processor_id();
  71         smp_store_cpu_info(cpu);
  72         cpu_data(cpu).x86_max_cores = 1;
  73         set_cpu_sibling_map(cpu);
  74
  75         xen_setup_cpu_clockevents();
  76
  77         set_cpu_online(cpu, true);
  78         percpu_write(cpu_state, CPU_ONLINE);
  79         wmb();
  80
  81         /* We can take interrupts now: we're officially "up". */
  82         local_irq_enable();
  83
  84         wmb();                  /* make sure everything is out */
  85 }
  86
  87 static __cpuinit void cpu_bringup_and_idle(void)
  88 {
  89         cpu_bringup();
  90         cpu_idle();
  91 }
  92
  93 static int xen_smp_intr_init(unsigned int cpu)
  94 {
  95         int rc;
  96         const char *resched_name, *callfunc_name, *debug_name;
  97
  98         resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
  99         rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
 100                                     cpu,
 101                                     xen_reschedule_interrupt,
 102                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 103                                     resched_name,
 104                                     NULL);
 105         if (rc < 0)
 106                 goto fail;
 107         per_cpu(xen_resched_irq, cpu) = rc;
 108
 109         callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
 110         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
 111                                     cpu,
 112                                     xen_call_function_interrupt,
 113                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 114                                     callfunc_name,
 115                                     NULL);
 116         if (rc < 0)
 117                 goto fail;
 118         per_cpu(xen_callfunc_irq, cpu) = rc;
 119
 120         debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
 121         rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
 122                                      IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
 123                                      debug_name, NULL);
 124         if (rc < 0)
 125                 goto fail;
 126         per_cpu(xen_debug_irq, cpu) = rc;
 127
 128         callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
 129         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
 130                                     cpu,
 131                                     xen_call_function_single_interrupt,
 132                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 133                                     callfunc_name,
 134                                     NULL);
 135         if (rc < 0)
 136                 goto fail;
 137         per_cpu(xen_callfuncsingle_irq, cpu) = rc;
 138
 139         return 0;
 140
 141  fail:
 142         if (per_cpu(xen_resched_irq, cpu) >= 0)
 143                 unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
 144         if (per_cpu(xen_callfunc_irq, cpu) >= 0)
 145                 unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
 146         if (per_cpu(xen_debug_irq, cpu) >= 0)
 147                 unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
 148         if (per_cpu(xen_callfuncsingle_irq, cpu) >= 0)
 149                 unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu),
 150                                        NULL);
 151
 152         return rc;
 153 }
 154
 155 static void __init xen_fill_possible_map(void)
 156 {
 157         int i, rc;
 158
 159         for (i = 0; i < nr_cpu_ids; i++) {
 160                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 161                 if (rc >= 0) {
 162                         num_processors++;
 163                         set_cpu_possible(i, true);
 164                 }
 165         }
 166 }
 167
 168 static void __init xen_smp_prepare_boot_cpu(void)
 169 {
 170         BUG_ON(smp_processor_id() != 0);
 171         native_smp_prepare_boot_cpu();
 172
 173         /* We've switched to the "real" per-cpu gdt, so make sure the
 174            old memory can be recycled */
 175         make_lowmem_page_readwrite(xen_initial_gdt);
 176
 177         xen_setup_vcpu_info_placement();
 178 }
 179
 180 static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 181 {
 182         unsigned cpu;
 183
 184         xen_init_lock_cpu(0);
 185
 186         smp_store_cpu_info(0);
 187         cpu_data(0).x86_max_cores = 1;
 188         set_cpu_sibling_map(0);
 189
 190         if (xen_smp_intr_init(0))
 191                 BUG();
 192
 193         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 194                 panic("could not allocate xen_cpu_initialized_map\n");
 195
 196         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 197
 198         /* Restrict the possible_map according to max_cpus. */
 199         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 200                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 201                         continue;
 202                 set_cpu_possible(cpu, false);
 203         }
 204
 205         for_each_possible_cpu (cpu) {
 206                 struct task_struct *idle;
 207
 208                 if (cpu == 0)
 209                         continue;
 210
 211                 idle = fork_idle(cpu);
 212                 if (IS_ERR(idle))
 213                         panic("failed fork for CPU %d", cpu);
 214
 215                 set_cpu_present(cpu, true);
 216         }
 217 }
 218
 219 static __cpuinit int
 220 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 221 {
 222         struct vcpu_guest_context *ctxt;
 223         struct desc_struct *gdt;
 224         unsigned long gdt_mfn;
 225
 226         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 227                 return 0;
 228
 229         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 230         if (ctxt == NULL)
 231                 return -ENOMEM;
 232
 233         gdt = get_cpu_gdt_table(cpu);
 234
 235         ctxt->flags = VGCF_IN_KERNEL;
 236         ctxt->user_regs.ds = __USER_DS;
 237         ctxt->user_regs.es = __USER_DS;
 238         ctxt->user_regs.ss = __KERNEL_DS;
 239 #ifdef CONFIG_X86_32
 240         ctxt->user_regs.fs = __KERNEL_PERCPU;
 241         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 242 #else
 243         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 244 #endif
 245         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 246         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 247
 248         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 249
 250         xen_copy_trap_info(ctxt->trap_ctxt);
 251
 252         ctxt->ldt_ents = 0;
 253
 254         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 255
 256         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 257         make_lowmem_page_readonly(gdt);
 258         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 259
 260         ctxt->gdt_frames[0] = gdt_mfn;
 261         ctxt->gdt_ents      = GDT_ENTRIES;
 262
 263         ctxt->user_regs.cs = __KERNEL_CS;
 264         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
 265
 266         ctxt->kernel_ss = __KERNEL_DS;
 267         ctxt->kernel_sp = idle->thread.sp0;
 268
 269 #ifdef CONFIG_X86_32
 270         ctxt->event_callback_cs     = __KERNEL_CS;
 271         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 272 #endif
 273         ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
 274         ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
 275
 276         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 277         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 278
 279         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
 280                 BUG();
 281
 282         kfree(ctxt);
 283         return 0;
 284 }
 285
 286 static int __cpuinit xen_cpu_up(unsigned int cpu)
 287 {
 288         struct task_struct *idle = idle_task(cpu);
 289         int rc;
 290
 291         per_cpu(current_task, cpu) = idle;
 292 #ifdef CONFIG_X86_32
 293         irq_ctx_init(cpu);
 294 #else
 295         clear_tsk_thread_flag(idle, TIF_FORK);
 296         per_cpu(kernel_stack, cpu) =
 297                 (unsigned long)task_stack_page(idle) -
 298                 KERNEL_STACK_OFFSET + THREAD_SIZE;
 299 #endif
 300         xen_setup_runstate_info(cpu);
 301         xen_setup_timer(cpu);
 302         xen_init_lock_cpu(cpu);
 303
 304         per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
 305
 306         /* make sure interrupts start blocked */
 307         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 308
 309         rc = cpu_initialize_context(cpu, idle);
 310         if (rc)
 311                 return rc;
 312
 313         if (num_online_cpus() == 1)
 314                 alternatives_smp_switch(1);
 315
 316         rc = xen_smp_intr_init(cpu);
 317         if (rc)
 318                 return rc;
 319
 320         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
 321         BUG_ON(rc);
 322
 323         while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
 324                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 325                 barrier();
 326         }
 327
 328         return 0;
 329 }
 330
 331 static void xen_smp_cpus_done(unsigned int max_cpus)
 332 {
 333 }
 334
 335 #ifdef CONFIG_HOTPLUG_CPU
 336 static int xen_cpu_disable(void)
 337 {
 338         unsigned int cpu = smp_processor_id();
 339         if (cpu == 0)
 340                 return -EBUSY;
 341
 342         cpu_disable_common();
 343
 344         load_cr3(swapper_pg_dir);
 345         return 0;
 346 }
 347
 348 static void xen_cpu_die(unsigned int cpu)
 349 {
 350         while (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL)) {
 351                 current->state = TASK_UNINTERRUPTIBLE;
 352                 schedule_timeout(HZ/10);
 353         }
 354         unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
 355         unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
 356         unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
 357         unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
 358         xen_uninit_lock_cpu(cpu);
 359         xen_teardown_timer(cpu);
 360
 361         if (num_online_cpus() == 1)
 362                 alternatives_smp_switch(0);
 363 }
 364
 365 static void __cpuinit xen_play_dead(void) /* used only with HOTPLUG_CPU */
 366 {
 367         play_dead_common();
 368         HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 369         cpu_bringup();
 370 }
 371
 372 #else /* !CONFIG_HOTPLUG_CPU */
 373 static int xen_cpu_disable(void)
 374 {
 375         return -ENOSYS;
 376 }
 377
 378 static void xen_cpu_die(unsigned int cpu)
 379 {
 380         BUG();
 381 }
 382
 383 static void xen_play_dead(void)
 384 {
 385         BUG();
 386 }
 387
 388 #endif
 389 static void stop_self(void *v)
 390 {
 391         int cpu = smp_processor_id();
 392
 393         /* make sure we're not pinning something down */
 394         load_cr3(swapper_pg_dir);
 395         /* should set up a minimal gdt */
 396
 397         HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
 398         BUG();
 399 }
 400
 401 static void xen_smp_send_stop(void)
 402 {
 403         smp_call_function(stop_self, NULL, 0);
 404 }
 405
 406 static void xen_smp_send_reschedule(int cpu)
 407 {
 408         xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
 409 }
 410
 411 static void xen_send_IPI_mask(const struct cpumask *mask,
 412                               enum ipi_vector vector)
 413 {
 414         unsigned cpu;
 415
 416         for_each_cpu_and(cpu, mask, cpu_online_mask)
 417                 xen_send_IPI_one(cpu, vector);
 418 }
 419
 420 static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
 421 {
 422         int cpu;
 423
 424         xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
 425
 426         /* Make sure other vcpus get a chance to run if they need to. */
 427         for_each_cpu(cpu, mask) {
 428                 if (xen_vcpu_stolen(cpu)) {
 429                         HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 430                         break;
 431                 }
 432         }
 433 }
 434
 435 static void xen_smp_send_call_function_single_ipi(int cpu)
 436 {
 437         xen_send_IPI_mask(cpumask_of(cpu),
 438                           XEN_CALL_FUNCTION_SINGLE_VECTOR);
 439 }
 440
 441 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
 442 {
 443         irq_enter();
 444         generic_smp_call_function_interrupt();
 445         inc_irq_stat(irq_call_count);
 446         irq_exit();
 447
 448         return IRQ_HANDLED;
 449 }
 450
 451 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
 452 {
 453         irq_enter();
 454         generic_smp_call_function_single_interrupt();
 455         inc_irq_stat(irq_call_count);
 456         irq_exit();
 457
 458         return IRQ_HANDLED;
 459 }
 460
 461 static const struct smp_ops xen_smp_ops __initdata = {
 462         .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
 463         .smp_prepare_cpus = xen_smp_prepare_cpus,
 464         .smp_cpus_done = xen_smp_cpus_done,
 465
 466         .cpu_up = xen_cpu_up,
 467         .cpu_die = xen_cpu_die,
 468         .cpu_disable = xen_cpu_disable,
 469         .play_dead = xen_play_dead,
 470
 471         .smp_send_stop = xen_smp_send_stop,
 472         .smp_send_reschedule = xen_smp_send_reschedule,
 473
 474         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 475         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 476 };
 477
 478 void __init xen_smp_init(void)
 479 {
 480         smp_ops = xen_smp_ops;
 481         xen_fill_possible_map();
 482         xen_init_spinlocks();
 483 }