arch/i386/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         xen_vcpu_setup(0);
 146
 147         /* We've switched to the "real" per-cpu gdt, so make sure the
 148            old memory can be recycled */
 149         make_lowmem_page_readwrite(&per_cpu__gdt_page);
 150
 151         for (cpu = 0; cpu < NR_CPUS; cpu++) {
 152                 cpus_clear(cpu_sibling_map[cpu]);
 153                 cpus_clear(cpu_core_map[cpu]);
 154         }
 155 }
 156
 157 void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 158 {
 159         unsigned cpu;
 160
 161         for (cpu = 0; cpu < NR_CPUS; cpu++) {
 162                 cpus_clear(cpu_sibling_map[cpu]);
 163                 cpus_clear(cpu_core_map[cpu]);
 164         }
 165
 166         smp_store_cpu_info(0);
 167         set_cpu_sibling_map(0);
 168
 169         if (xen_smp_intr_init(0))
 170                 BUG();
 171
 172         cpu_initialized_map = cpumask_of_cpu(0);
 173
 174         /* Restrict the possible_map according to max_cpus. */
 175         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 176                 for (cpu = NR_CPUS-1; !cpu_isset(cpu, cpu_possible_map); cpu--)
 177                         continue;
 178                 cpu_clear(cpu, cpu_possible_map);
 179         }
 180
 181         for_each_possible_cpu (cpu) {
 182                 struct task_struct *idle;
 183
 184                 if (cpu == 0)
 185                         continue;
 186
 187                 idle = fork_idle(cpu);
 188                 if (IS_ERR(idle))
 189                         panic("failed fork for CPU %d", cpu);
 190
 191                 cpu_set(cpu, cpu_present_map);
 192         }
 193
 194         //init_xenbus_allowed_cpumask();
 195 }
 196
 197 static __cpuinit int
 198 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 199 {
 200         struct vcpu_guest_context *ctxt;
 201         struct gdt_page *gdt = &per_cpu(gdt_page, cpu);
 202
 203         if (cpu_test_and_set(cpu, cpu_initialized_map))
 204                 return 0;
 205
 206         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 207         if (ctxt == NULL)
 208                 return -ENOMEM;
 209
 210         ctxt->flags = VGCF_IN_KERNEL;
 211         ctxt->user_regs.ds = __USER_DS;
 212         ctxt->user_regs.es = __USER_DS;
 213         ctxt->user_regs.fs = __KERNEL_PERCPU;
 214         ctxt->user_regs.gs = 0;
 215         ctxt->user_regs.ss = __KERNEL_DS;
 216         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 217         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 218
 219         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 220
 221         xen_copy_trap_info(ctxt->trap_ctxt);
 222
 223         ctxt->ldt_ents = 0;
 224
 225         BUG_ON((unsigned long)gdt->gdt & ~PAGE_MASK);
 226         make_lowmem_page_readonly(gdt->gdt);
 227
 228         ctxt->gdt_frames[0] = virt_to_mfn(gdt->gdt);
 229         ctxt->gdt_ents      = ARRAY_SIZE(gdt->gdt);
 230
 231         ctxt->user_regs.cs = __KERNEL_CS;
 232         ctxt->user_regs.esp = idle->thread.esp0 - sizeof(struct pt_regs);
 233
 234         ctxt->kernel_ss = __KERNEL_DS;
 235         ctxt->kernel_sp = idle->thread.esp0;
 236
 237         ctxt->event_callback_cs     = __KERNEL_CS;
 238         ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
 239         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 240         ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
 241
 242         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 243         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 244
 245         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
 246                 BUG();
 247
 248         kfree(ctxt);
 249         return 0;
 250 }
 251
 252 int __cpuinit xen_cpu_up(unsigned int cpu)
 253 {
 254         struct task_struct *idle = idle_task(cpu);
 255         int rc;
 256
 257 #if 0
 258         rc = cpu_up_check(cpu);
 259         if (rc)
 260                 return rc;
 261 #endif
 262
 263         init_gdt(cpu);
 264         per_cpu(current_task, cpu) = idle;
 265         xen_vcpu_setup(cpu);
 266         irq_ctx_init(cpu);
 267         xen_setup_timer(cpu);
 268
 269         /* make sure interrupts start blocked */
 270         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 271
 272         rc = cpu_initialize_context(cpu, idle);
 273         if (rc)
 274                 return rc;
 275
 276         if (num_online_cpus() == 1)
 277                 alternatives_smp_switch(1);
 278
 279         rc = xen_smp_intr_init(cpu);
 280         if (rc)
 281                 return rc;
 282
 283         smp_store_cpu_info(cpu);
 284         set_cpu_sibling_map(cpu);
 285         /* This must be done before setting cpu_online_map */
 286         wmb();
 287
 288         cpu_set(cpu, cpu_online_map);
 289
 290         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
 291         BUG_ON(rc);
 292
 293         return 0;
 294 }
 295
 296 void xen_smp_cpus_done(unsigned int max_cpus)
 297 {
 298 }
 299
 300 static void stop_self(void *v)
 301 {
 302         int cpu = smp_processor_id();
 303
 304         /* make sure we're not pinning something down */
 305         load_cr3(swapper_pg_dir);
 306         /* should set up a minimal gdt */
 307
 308         HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
 309         BUG();
 310 }
 311
 312 void xen_smp_send_stop(void)
 313 {
 314         smp_call_function(stop_self, NULL, 0, 0);
 315 }
 316
 317 void xen_smp_send_reschedule(int cpu)
 318 {
 319         xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
 320 }
 321
 322
 323 static void xen_send_IPI_mask(cpumask_t mask, enum ipi_vector vector)
 324 {
 325         unsigned cpu;
 326
 327         cpus_and(mask, mask, cpu_online_map);
 328
 329         for_each_cpu_mask(cpu, mask)
 330                 xen_send_IPI_one(cpu, vector);
 331 }
 332
 333 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
 334 {
 335         void (*func) (void *info) = call_data->func;
 336         void *info = call_data->info;
 337         int wait = call_data->wait;
 338
 339         /*
 340          * Notify initiating CPU that I've grabbed the data and am
 341          * about to execute the function
 342          */
 343         mb();
 344         atomic_inc(&call_data->started);
 345         /*
 346          * At this point the info structure may be out of scope unless wait==1
 347          */
 348         irq_enter();
 349         (*func)(info);
 350         irq_exit();
 351
 352         if (wait) {
 353                 mb();           /* commit everything before setting finished */
 354                 atomic_inc(&call_data->finished);
 355         }
 356
 357         return IRQ_HANDLED;
 358 }
 359
 360 int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *),
 361                                void *info, int wait)
 362 {
 363         struct call_data_struct data;
 364         int cpus;
 365
 366         /* Holding any lock stops cpus from going down. */
 367         spin_lock(&call_lock);
 368
 369         cpu_clear(smp_processor_id(), mask);
 370
 371         cpus = cpus_weight(mask);
 372         if (!cpus) {
 373                 spin_unlock(&call_lock);
 374                 return 0;
 375         }
 376
 377         /* Can deadlock when called with interrupts disabled */
 378         WARN_ON(irqs_disabled());
 379
 380         data.func = func;
 381         data.info = info;
 382         atomic_set(&data.started, 0);
 383         data.wait = wait;
 384         if (wait)
 385                 atomic_set(&data.finished, 0);
 386
 387         call_data = &data;
 388         mb();                   /* write everything before IPI */
 389
 390         /* Send a message to other CPUs and wait for them to respond */
 391         xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
 392
 393         /* Make sure other vcpus get a chance to run.
 394            XXX too severe?  Maybe we should check the other CPU's states? */
 395         HYPERVISOR_sched_op(SCHEDOP_yield, 0);
 396
 397         /* Wait for response */
 398         while (atomic_read(&data.started) != cpus ||
 399                (wait && atomic_read(&data.finished) != cpus))
 400                 cpu_relax();
 401
 402         spin_unlock(&call_lock);
 403
 404         return 0;
 405 }