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