1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Xen SMP support 4 * 5 * This file implements the Xen versions of smp_ops. SMP under Xen is 6 * very straightforward. Bringing a CPU up is simply a matter of 7 * loading its initial context and setting it running. 8 * 9 * IPIs are handled through the Xen event mechanism. 10 * 11 * Because virtual CPUs can be scheduled onto any real CPU, there's no 12 * useful topology information for the kernel to make use of. As a 13 * result, all CPUs are treated as if they're single-core and 14 * single-threaded. 15 */ 16 #include <linux/sched.h> 17 #include <linux/sched/task_stack.h> 18 #include <linux/err.h> 19 #include <linux/slab.h> 20 #include <linux/smp.h> 21 #include <linux/irq_work.h> 22 #include <linux/tick.h> 23 #include <linux/nmi.h> 24 #include <linux/cpuhotplug.h> 25 #include <linux/stackprotector.h> 26 27 #include <asm/paravirt.h> 28 #include <asm/desc.h> 29 #include <asm/pgtable.h> 30 #include <asm/cpu.h> 31 32 #include <xen/interface/xen.h> 33 #include <xen/interface/vcpu.h> 34 #include <xen/interface/xenpmu.h> 35 36 #include <asm/spec-ctrl.h> 37 #include <asm/xen/interface.h> 38 #include <asm/xen/hypercall.h> 39 40 #include <xen/xen.h> 41 #include <xen/page.h> 42 #include <xen/events.h> 43 44 #include <xen/hvc-console.h> 45 #include "xen-ops.h" 46 #include "mmu.h" 47 #include "smp.h" 48 #include "pmu.h" 49 50 cpumask_var_t xen_cpu_initialized_map; 51 52 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 }; 53 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 }; 54 55 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id); 56 57 static void cpu_bringup(void) 58 { 59 int cpu; 60 61 cr4_init(); 62 cpu_init(); 63 touch_softlockup_watchdog(); 64 preempt_disable(); 65 66 /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */ 67 if (!xen_feature(XENFEAT_supervisor_mode_kernel)) { 68 xen_enable_sysenter(); 69 xen_enable_syscall(); 70 } 71 cpu = smp_processor_id(); 72 smp_store_cpu_info(cpu); 73 cpu_data(cpu).x86_max_cores = 1; 74 set_cpu_sibling_map(cpu); 75 76 speculative_store_bypass_ht_init(); 77 78 xen_setup_cpu_clockevents(); 79 80 notify_cpu_starting(cpu); 81 82 set_cpu_online(cpu, true); 83 84 cpu_set_state_online(cpu); /* Implies full memory barrier. */ 85 86 /* We can take interrupts now: we're officially "up". */ 87 local_irq_enable(); 88 } 89 90 asmlinkage __visible void cpu_bringup_and_idle(void) 91 { 92 cpu_bringup(); 93 boot_init_stack_canary(); 94 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); 95 } 96 97 void xen_smp_intr_free_pv(unsigned int cpu) 98 { 99 if (per_cpu(xen_irq_work, cpu).irq >= 0) { 100 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL); 101 per_cpu(xen_irq_work, cpu).irq = -1; 102 kfree(per_cpu(xen_irq_work, cpu).name); 103 per_cpu(xen_irq_work, cpu).name = NULL; 104 } 105 106 if (per_cpu(xen_pmu_irq, cpu).irq >= 0) { 107 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL); 108 per_cpu(xen_pmu_irq, cpu).irq = -1; 109 kfree(per_cpu(xen_pmu_irq, cpu).name); 110 per_cpu(xen_pmu_irq, cpu).name = NULL; 111 } 112 } 113 114 int xen_smp_intr_init_pv(unsigned int cpu) 115 { 116 int rc; 117 char *callfunc_name, *pmu_name; 118 119 callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu); 120 rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR, 121 cpu, 122 xen_irq_work_interrupt, 123 IRQF_PERCPU|IRQF_NOBALANCING, 124 callfunc_name, 125 NULL); 126 if (rc < 0) 127 goto fail; 128 per_cpu(xen_irq_work, cpu).irq = rc; 129 per_cpu(xen_irq_work, cpu).name = callfunc_name; 130 131 if (is_xen_pmu(cpu)) { 132 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu); 133 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu, 134 xen_pmu_irq_handler, 135 IRQF_PERCPU|IRQF_NOBALANCING, 136 pmu_name, NULL); 137 if (rc < 0) 138 goto fail; 139 per_cpu(xen_pmu_irq, cpu).irq = rc; 140 per_cpu(xen_pmu_irq, cpu).name = pmu_name; 141 } 142 143 return 0; 144 145 fail: 146 xen_smp_intr_free_pv(cpu); 147 return rc; 148 } 149 150 static void __init xen_fill_possible_map(void) 151 { 152 int i, rc; 153 154 if (xen_initial_domain()) 155 return; 156 157 for (i = 0; i < nr_cpu_ids; i++) { 158 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL); 159 if (rc >= 0) { 160 num_processors++; 161 set_cpu_possible(i, true); 162 } 163 } 164 } 165 166 static void __init xen_filter_cpu_maps(void) 167 { 168 int i, rc; 169 unsigned int subtract = 0; 170 171 if (!xen_initial_domain()) 172 return; 173 174 num_processors = 0; 175 disabled_cpus = 0; 176 for (i = 0; i < nr_cpu_ids; i++) { 177 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL); 178 if (rc >= 0) { 179 num_processors++; 180 set_cpu_possible(i, true); 181 } else { 182 set_cpu_possible(i, false); 183 set_cpu_present(i, false); 184 subtract++; 185 } 186 } 187 #ifdef CONFIG_HOTPLUG_CPU 188 /* This is akin to using 'nr_cpus' on the Linux command line. 189 * Which is OK as when we use 'dom0_max_vcpus=X' we can only 190 * have up to X, while nr_cpu_ids is greater than X. This 191 * normally is not a problem, except when CPU hotplugging 192 * is involved and then there might be more than X CPUs 193 * in the guest - which will not work as there is no 194 * hypercall to expand the max number of VCPUs an already 195 * running guest has. So cap it up to X. */ 196 if (subtract) 197 nr_cpu_ids = nr_cpu_ids - subtract; 198 #endif 199 200 } 201 202 static void __init xen_pv_smp_prepare_boot_cpu(void) 203 { 204 BUG_ON(smp_processor_id() != 0); 205 native_smp_prepare_boot_cpu(); 206 207 if (!xen_feature(XENFEAT_writable_page_tables)) 208 /* We've switched to the "real" per-cpu gdt, so make 209 * sure the old memory can be recycled. */ 210 make_lowmem_page_readwrite(xen_initial_gdt); 211 212 #ifdef CONFIG_X86_32 213 /* 214 * Xen starts us with XEN_FLAT_RING1_DS, but linux code 215 * expects __USER_DS 216 */ 217 loadsegment(ds, __USER_DS); 218 loadsegment(es, __USER_DS); 219 #endif 220 221 xen_filter_cpu_maps(); 222 xen_setup_vcpu_info_placement(); 223 224 /* 225 * The alternative logic (which patches the unlock/lock) runs before 226 * the smp bootup up code is activated. Hence we need to set this up 227 * the core kernel is being patched. Otherwise we will have only 228 * modules patched but not core code. 229 */ 230 xen_init_spinlocks(); 231 } 232 233 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus) 234 { 235 unsigned cpu; 236 unsigned int i; 237 238 if (skip_ioapic_setup) { 239 char *m = (max_cpus == 0) ? 240 "The nosmp parameter is incompatible with Xen; " \ 241 "use Xen dom0_max_vcpus=1 parameter" : 242 "The noapic parameter is incompatible with Xen"; 243 244 xen_raw_printk(m); 245 panic(m); 246 } 247 xen_init_lock_cpu(0); 248 249 smp_store_boot_cpu_info(); 250 cpu_data(0).x86_max_cores = 1; 251 252 for_each_possible_cpu(i) { 253 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL); 254 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL); 255 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL); 256 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL); 257 } 258 set_cpu_sibling_map(0); 259 260 speculative_store_bypass_ht_init(); 261 262 xen_pmu_init(0); 263 264 if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0)) 265 BUG(); 266 267 if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL)) 268 panic("could not allocate xen_cpu_initialized_map\n"); 269 270 cpumask_copy(xen_cpu_initialized_map, cpumask_of(0)); 271 272 /* Restrict the possible_map according to max_cpus. */ 273 while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) { 274 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--) 275 continue; 276 set_cpu_possible(cpu, false); 277 } 278 279 for_each_possible_cpu(cpu) 280 set_cpu_present(cpu, true); 281 } 282 283 static int 284 cpu_initialize_context(unsigned int cpu, struct task_struct *idle) 285 { 286 struct vcpu_guest_context *ctxt; 287 struct desc_struct *gdt; 288 unsigned long gdt_mfn; 289 290 /* used to tell cpu_init() that it can proceed with initialization */ 291 cpumask_set_cpu(cpu, cpu_callout_mask); 292 if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map)) 293 return 0; 294 295 ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL); 296 if (ctxt == NULL) 297 return -ENOMEM; 298 299 gdt = get_cpu_gdt_rw(cpu); 300 301 #ifdef CONFIG_X86_32 302 ctxt->user_regs.fs = __KERNEL_PERCPU; 303 ctxt->user_regs.gs = __KERNEL_STACK_CANARY; 304 #endif 305 memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt)); 306 307 /* 308 * Bring up the CPU in cpu_bringup_and_idle() with the stack 309 * pointing just below where pt_regs would be if it were a normal 310 * kernel entry. 311 */ 312 ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle; 313 ctxt->flags = VGCF_IN_KERNEL; 314 ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */ 315 ctxt->user_regs.ds = __USER_DS; 316 ctxt->user_regs.es = __USER_DS; 317 ctxt->user_regs.ss = __KERNEL_DS; 318 ctxt->user_regs.cs = __KERNEL_CS; 319 ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle); 320 321 xen_copy_trap_info(ctxt->trap_ctxt); 322 323 ctxt->ldt_ents = 0; 324 325 BUG_ON((unsigned long)gdt & ~PAGE_MASK); 326 327 gdt_mfn = arbitrary_virt_to_mfn(gdt); 328 make_lowmem_page_readonly(gdt); 329 make_lowmem_page_readonly(mfn_to_virt(gdt_mfn)); 330 331 ctxt->gdt_frames[0] = gdt_mfn; 332 ctxt->gdt_ents = GDT_ENTRIES; 333 334 /* 335 * Set SS:SP that Xen will use when entering guest kernel mode 336 * from guest user mode. Subsequent calls to load_sp0() can 337 * change this value. 338 */ 339 ctxt->kernel_ss = __KERNEL_DS; 340 ctxt->kernel_sp = task_top_of_stack(idle); 341 342 #ifdef CONFIG_X86_32 343 ctxt->event_callback_cs = __KERNEL_CS; 344 ctxt->failsafe_callback_cs = __KERNEL_CS; 345 #else 346 ctxt->gs_base_kernel = per_cpu_offset(cpu); 347 #endif 348 ctxt->event_callback_eip = 349 (unsigned long)xen_hypervisor_callback; 350 ctxt->failsafe_callback_eip = 351 (unsigned long)xen_failsafe_callback; 352 per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir); 353 354 ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir)); 355 if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt)) 356 BUG(); 357 358 kfree(ctxt); 359 return 0; 360 } 361 362 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle) 363 { 364 int rc; 365 366 rc = common_cpu_up(cpu, idle); 367 if (rc) 368 return rc; 369 370 xen_setup_runstate_info(cpu); 371 372 /* 373 * PV VCPUs are always successfully taken down (see 'while' loop 374 * in xen_cpu_die()), so -EBUSY is an error. 375 */ 376 rc = cpu_check_up_prepare(cpu); 377 if (rc) 378 return rc; 379 380 /* make sure interrupts start blocked */ 381 per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1; 382 383 rc = cpu_initialize_context(cpu, idle); 384 if (rc) 385 return rc; 386 387 xen_pmu_init(cpu); 388 389 rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL); 390 BUG_ON(rc); 391 392 while (cpu_report_state(cpu) != CPU_ONLINE) 393 HYPERVISOR_sched_op(SCHEDOP_yield, NULL); 394 395 return 0; 396 } 397 398 #ifdef CONFIG_HOTPLUG_CPU 399 static int xen_pv_cpu_disable(void) 400 { 401 unsigned int cpu = smp_processor_id(); 402 if (cpu == 0) 403 return -EBUSY; 404 405 cpu_disable_common(); 406 407 load_cr3(swapper_pg_dir); 408 return 0; 409 } 410 411 static void xen_pv_cpu_die(unsigned int cpu) 412 { 413 while (HYPERVISOR_vcpu_op(VCPUOP_is_up, 414 xen_vcpu_nr(cpu), NULL)) { 415 __set_current_state(TASK_UNINTERRUPTIBLE); 416 schedule_timeout(HZ/10); 417 } 418 419 if (common_cpu_die(cpu) == 0) { 420 xen_smp_intr_free(cpu); 421 xen_uninit_lock_cpu(cpu); 422 xen_teardown_timer(cpu); 423 xen_pmu_finish(cpu); 424 } 425 } 426 427 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */ 428 { 429 play_dead_common(); 430 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL); 431 cpu_bringup(); 432 /* 433 * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down) 434 * clears certain data that the cpu_idle loop (which called us 435 * and that we return from) expects. The only way to get that 436 * data back is to call: 437 */ 438 tick_nohz_idle_enter(); 439 tick_nohz_idle_stop_tick_protected(); 440 441 cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE); 442 } 443 444 #else /* !CONFIG_HOTPLUG_CPU */ 445 static int xen_pv_cpu_disable(void) 446 { 447 return -ENOSYS; 448 } 449 450 static void xen_pv_cpu_die(unsigned int cpu) 451 { 452 BUG(); 453 } 454 455 static void xen_pv_play_dead(void) 456 { 457 BUG(); 458 } 459 460 #endif 461 static void stop_self(void *v) 462 { 463 int cpu = smp_processor_id(); 464 465 /* make sure we're not pinning something down */ 466 load_cr3(swapper_pg_dir); 467 /* should set up a minimal gdt */ 468 469 set_cpu_online(cpu, false); 470 471 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL); 472 BUG(); 473 } 474 475 static void xen_pv_stop_other_cpus(int wait) 476 { 477 smp_call_function(stop_self, NULL, wait); 478 } 479 480 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id) 481 { 482 irq_enter(); 483 irq_work_run(); 484 inc_irq_stat(apic_irq_work_irqs); 485 irq_exit(); 486 487 return IRQ_HANDLED; 488 } 489 490 static const struct smp_ops xen_smp_ops __initconst = { 491 .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu, 492 .smp_prepare_cpus = xen_pv_smp_prepare_cpus, 493 .smp_cpus_done = xen_smp_cpus_done, 494 495 .cpu_up = xen_pv_cpu_up, 496 .cpu_die = xen_pv_cpu_die, 497 .cpu_disable = xen_pv_cpu_disable, 498 .play_dead = xen_pv_play_dead, 499 500 .stop_other_cpus = xen_pv_stop_other_cpus, 501 .smp_send_reschedule = xen_smp_send_reschedule, 502 503 .send_call_func_ipi = xen_smp_send_call_function_ipi, 504 .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi, 505 }; 506 507 void __init xen_smp_init(void) 508 { 509 smp_ops = xen_smp_ops; 510 xen_fill_possible_map(); 511 } 512