arch/x86/xen/smp.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  * This does not handle HOTPLUG_CPU yet.
  16  */
  17 #include <linux/sched.h>
  18 #include <linux/err.h>
  19 #include <linux/smp.h>
  20
  21 #include <asm/paravirt.h>
  22 #include <asm/desc.h>
  23 #include <asm/pgtable.h>
  24 #include <asm/cpu.h>
  25
  26 #include <xen/interface/xen.h>
  27 #include <xen/interface/vcpu.h>
  28
  29 #include <asm/xen/interface.h>
  30 #include <asm/xen/hypercall.h>
  31
  32 #include <xen/page.h>
  33 #include <xen/events.h>
  34
  35 #include "xen-ops.h"
  36 #include "mmu.h"
  37
  38 cpumask_t xen_cpu_initialized_map;
  39 static DEFINE_PER_CPU(int, resched_irq) = -1;
  40 static DEFINE_PER_CPU(int, callfunc_irq) = -1;
  41 static DEFINE_PER_CPU(int, debug_irq) = -1;
  42
  43 /*
  44  * Structure and data for smp_call_function(). This is designed to minimise
  45  * static memory requirements. It also looks cleaner.
  46  */
  47 static DEFINE_SPINLOCK(call_lock);
  48
  49 struct call_data_struct {
  50         void (*func) (void *info);
  51         void *info;
  52         atomic_t started;
  53         atomic_t finished;
  54         int wait;
  55 };
  56
  57 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
  58
  59 static struct call_data_struct *call_data;
  60
  61 /*
  62  * Reschedule call back. Nothing to do,
  63  * all the work is done automatically when
  64  * we return from the interrupt.
  65  */
  66 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
  67 {
  68 #ifdef CONFIG_X86_32
  69         __get_cpu_var(irq_stat).irq_resched_count++;
  70 #else
  71         add_pda(irq_resched_count, 1);
  72 #endif
  73
  74         return IRQ_HANDLED;
  75 }
  76
  77 static __cpuinit void cpu_bringup_and_idle(void)
  78 {
  79         int cpu = smp_processor_id();
  80
  81         cpu_init();
  82         xen_enable_sysenter();
  83
  84         preempt_disable();
  85         per_cpu(cpu_state, cpu) = CPU_ONLINE;
  86
  87         xen_setup_cpu_clockevents();
  88
  89         /* We can take interrupts now: we're officially "up". */
  90         local_irq_enable();
  91
  92         wmb();                  /* make sure everything is out */
  93         cpu_idle();
  94 }
  95
  96 static int xen_smp_intr_init(unsigned int cpu)
  97 {
  98         int rc;
  99         const char *resched_name, *callfunc_name, *debug_name;
 100
 101         resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
 102         rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
 103                                     cpu,
 104                                     xen_reschedule_interrupt,
 105                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 106                                     resched_name,
 107                                     NULL);
 108         if (rc < 0)
 109                 goto fail;
 110         per_cpu(resched_irq, cpu) = rc;
 111
 112         callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
 113         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
 114                                     cpu,
 115                                     xen_call_function_interrupt,
 116                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 117                                     callfunc_name,
 118                                     NULL);
 119         if (rc < 0)
 120                 goto fail;
 121         per_cpu(callfunc_irq, cpu) = rc;
 122
 123         debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
 124         rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
 125                                      IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
 126                                      debug_name, NULL);
 127         if (rc < 0)
 128                 goto fail;
 129         per_cpu(debug_irq, cpu) = rc;
 130
 131         return 0;
 132
 133  fail:
 134         if (per_cpu(resched_irq, cpu) >= 0)
 135                 unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
 136         if (per_cpu(callfunc_irq, cpu) >= 0)
 137                 unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
 138         if (per_cpu(debug_irq, cpu) >= 0)
 139                 unbind_from_irqhandler(per_cpu(debug_irq, cpu), NULL);
 140         return rc;
 141 }
 142
 143 void __init xen_fill_possible_map(void)
 144 {
 145         int i, rc;
 146
 147         for (i = 0; i < NR_CPUS; i++) {
 148                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 149                 if (rc >= 0)
 150                         cpu_set(i, cpu_possible_map);
 151         }
 152 }
 153
 154 void __init xen_smp_prepare_boot_cpu(void)
 155 {
 156         int cpu;
 157
 158         BUG_ON(smp_processor_id() != 0);
 159         native_smp_prepare_boot_cpu();
 160
 161         /* We've switched to the "real" per-cpu gdt, so make sure the
 162            old memory can be recycled */
 163         make_lowmem_page_readwrite(&per_cpu__gdt_page);
 164
 165         for_each_possible_cpu(cpu) {
 166                 cpus_clear(per_cpu(cpu_sibling_map, cpu));
 167                 /*
 168                  * cpu_core_map lives in a per cpu area that is cleared
 169                  * when the per cpu array is allocated.
 170                  *
 171                  * cpus_clear(per_cpu(cpu_core_map, cpu));
 172                  */
 173         }
 174
 175         xen_setup_vcpu_info_placement();
 176 }
 177
 178 void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 179 {
 180         unsigned cpu;
 181
 182         for_each_possible_cpu(cpu) {
 183                 cpus_clear(per_cpu(cpu_sibling_map, cpu));
 184                 /*
 185                  * cpu_core_ map will be zeroed when the per
 186                  * cpu area is allocated.
 187                  *
 188                  * cpus_clear(per_cpu(cpu_core_map, cpu));
 189                  */
 190         }
 191
 192         smp_store_cpu_info(0);
 193         set_cpu_sibling_map(0);
 194
 195         if (xen_smp_intr_init(0))
 196                 BUG();
 197
 198         xen_cpu_initialized_map = cpumask_of_cpu(0);
 199
 200         /* Restrict the possible_map according to max_cpus. */
 201         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 202                 for (cpu = NR_CPUS - 1; !cpu_possible(cpu); cpu--)
 203                         continue;
 204                 cpu_clear(cpu, cpu_possible_map);
 205         }
 206
 207         for_each_possible_cpu (cpu) {
 208                 struct task_struct *idle;
 209
 210                 if (cpu == 0)
 211                         continue;
 212
 213                 idle = fork_idle(cpu);
 214                 if (IS_ERR(idle))
 215                         panic("failed fork for CPU %d", cpu);
 216
 217                 cpu_set(cpu, cpu_present_map);
 218         }
 219
 220         //init_xenbus_allowed_cpumask();
 221 }
 222
 223 static __cpuinit int
 224 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 225 {
 226         struct vcpu_guest_context *ctxt;
 227         struct gdt_page *gdt = &per_cpu(gdt_page, cpu);
 228
 229         if (cpu_test_and_set(cpu, xen_cpu_initialized_map))
 230                 return 0;
 231
 232         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 233         if (ctxt == NULL)
 234                 return -ENOMEM;
 235
 236         ctxt->flags = VGCF_IN_KERNEL;
 237         ctxt->user_regs.ds = __USER_DS;
 238         ctxt->user_regs.es = __USER_DS;
 239         ctxt->user_regs.fs = __KERNEL_PERCPU;
 240         ctxt->user_regs.gs = 0;
 241         ctxt->user_regs.ss = __KERNEL_DS;
 242         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 243         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 244
 245         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 246
 247         xen_copy_trap_info(ctxt->trap_ctxt);
 248
 249         ctxt->ldt_ents = 0;
 250
 251         BUG_ON((unsigned long)gdt->gdt & ~PAGE_MASK);
 252         make_lowmem_page_readonly(gdt->gdt);
 253
 254         ctxt->gdt_frames[0] = virt_to_mfn(gdt->gdt);
 255         ctxt->gdt_ents      = ARRAY_SIZE(gdt->gdt);
 256
 257         ctxt->user_regs.cs = __KERNEL_CS;
 258         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
 259
 260         ctxt->kernel_ss = __KERNEL_DS;
 261         ctxt->kernel_sp = idle->thread.sp0;
 262
 263         ctxt->event_callback_cs     = __KERNEL_CS;
 264         ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
 265         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 266         ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
 267
 268         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 269         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 270
 271         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
 272                 BUG();
 273
 274         kfree(ctxt);
 275         return 0;
 276 }
 277
 278 int __cpuinit xen_cpu_up(unsigned int cpu)
 279 {
 280         struct task_struct *idle = idle_task(cpu);
 281         int rc;
 282
 283 #if 0
 284         rc = cpu_up_check(cpu);
 285         if (rc)
 286                 return rc;
 287 #endif
 288
 289         init_gdt(cpu);
 290         per_cpu(current_task, cpu) = idle;
 291         irq_ctx_init(cpu);
 292         xen_setup_timer(cpu);
 293
 294         /* make sure interrupts start blocked */
 295         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 296
 297         rc = cpu_initialize_context(cpu, idle);
 298         if (rc)
 299                 return rc;
 300
 301         if (num_online_cpus() == 1)
 302                 alternatives_smp_switch(1);
 303
 304         rc = xen_smp_intr_init(cpu);
 305         if (rc)
 306                 return rc;
 307
 308         smp_store_cpu_info(cpu);
 309         set_cpu_sibling_map(cpu);
 310         /* This must be done before setting cpu_online_map */
 311         wmb();
 312
 313         cpu_set(cpu, cpu_online_map);
 314
 315         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
 316         BUG_ON(rc);
 317
 318         return 0;
 319 }
 320
 321 void xen_smp_cpus_done(unsigned int max_cpus)
 322 {
 323 }
 324
 325 static void stop_self(void *v)
 326 {
 327         int cpu = smp_processor_id();
 328
 329         /* make sure we're not pinning something down */
 330         load_cr3(swapper_pg_dir);
 331         /* should set up a minimal gdt */
 332
 333         HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
 334         BUG();
 335 }
 336
 337 void xen_smp_send_stop(void)
 338 {
 339         smp_call_function(stop_self, NULL, 0, 0);
 340 }
 341
 342 void xen_smp_send_reschedule(int cpu)
 343 {
 344         xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
 345 }
 346
 347
 348 static void xen_send_IPI_mask(cpumask_t mask, enum ipi_vector vector)
 349 {
 350         unsigned cpu;
 351
 352         cpus_and(mask, mask, cpu_online_map);
 353
 354         for_each_cpu_mask(cpu, mask)
 355                 xen_send_IPI_one(cpu, vector);
 356 }
 357
 358 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
 359 {
 360         void (*func) (void *info) = call_data->func;
 361         void *info = call_data->info;
 362         int wait = call_data->wait;
 363
 364         /*
 365          * Notify initiating CPU that I've grabbed the data and am
 366          * about to execute the function
 367          */
 368         mb();
 369         atomic_inc(&call_data->started);
 370         /*
 371          * At this point the info structure may be out of scope unless wait==1
 372          */
 373         irq_enter();
 374         (*func)(info);
 375         __get_cpu_var(irq_stat).irq_call_count++;
 376         irq_exit();
 377
 378         if (wait) {
 379                 mb();           /* commit everything before setting finished */
 380                 atomic_inc(&call_data->finished);
 381         }
 382
 383         return IRQ_HANDLED;
 384 }
 385
 386 int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *),
 387                                void *info, int wait)
 388 {
 389         struct call_data_struct data;
 390         int cpus, cpu;
 391         bool yield;
 392
 393         /* Holding any lock stops cpus from going down. */
 394         spin_lock(&call_lock);
 395
 396         cpu_clear(smp_processor_id(), mask);
 397
 398         cpus = cpus_weight(mask);
 399         if (!cpus) {
 400                 spin_unlock(&call_lock);
 401                 return 0;
 402         }
 403
 404         /* Can deadlock when called with interrupts disabled */
 405         WARN_ON(irqs_disabled());
 406
 407         data.func = func;
 408         data.info = info;
 409         atomic_set(&data.started, 0);
 410         data.wait = wait;
 411         if (wait)
 412                 atomic_set(&data.finished, 0);
 413
 414         call_data = &data;
 415         mb();                   /* write everything before IPI */
 416
 417         /* Send a message to other CPUs and wait for them to respond */
 418         xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
 419
 420         /* Make sure other vcpus get a chance to run if they need to. */
 421         yield = false;
 422         for_each_cpu_mask(cpu, mask)
 423                 if (xen_vcpu_stolen(cpu))
 424                         yield = true;
 425
 426         if (yield)
 427                 HYPERVISOR_sched_op(SCHEDOP_yield, 0);
 428
 429         /* Wait for response */
 430         while (atomic_read(&data.started) != cpus ||
 431                (wait && atomic_read(&data.finished) != cpus))
 432                 cpu_relax();
 433
 434         spin_unlock(&call_lock);
 435
 436         return 0;
 437 }