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