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 } 422