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 #include <linux/pgtable.h> 27 28 #include <asm/paravirt.h> 29 #include <asm/idtentry.h> 30 #include <asm/desc.h> 31 #include <asm/cpu.h> 32 #include <asm/apic.h> 33 #include <asm/io_apic.h> 34 35 #include <xen/interface/xen.h> 36 #include <xen/interface/vcpu.h> 37 #include <xen/interface/xenpmu.h> 38 39 #include <asm/spec-ctrl.h> 40 #include <asm/xen/interface.h> 41 #include <asm/xen/hypercall.h> 42 43 #include <xen/xen.h> 44 #include <xen/page.h> 45 #include <xen/events.h> 46 47 #include <xen/hvc-console.h> 48 #include "xen-ops.h" 49 #include "mmu.h" 50 #include "smp.h" 51 #include "pmu.h" 52 53 cpumask_var_t xen_cpu_initialized_map; 54 55 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 }; 56 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 }; 57 58 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id); 59 60 static void cpu_bringup(void) 61 { 62 int cpu; 63 64 cr4_init(); 65 cpuhp_ap_sync_alive(); 66 cpu_init(); 67 fpu__init_cpu(); 68 touch_softlockup_watchdog(); 69 70 /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */ 71 if (!xen_feature(XENFEAT_supervisor_mode_kernel)) { 72 xen_enable_sysenter(); 73 xen_enable_syscall(); 74 } 75 cpu = smp_processor_id(); 76 smp_store_cpu_info(cpu); 77 set_cpu_sibling_map(cpu); 78 79 speculative_store_bypass_ht_init(); 80 81 xen_setup_cpu_clockevents(); 82 83 notify_cpu_starting(cpu); 84 85 set_cpu_online(cpu, true); 86 87 smp_mb(); 88 89 /* We can take interrupts now: we're officially "up". */ 90 local_irq_enable(); 91 } 92 93 asmlinkage __visible void cpu_bringup_and_idle(void) 94 { 95 cpu_bringup(); 96 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); 97 } 98 99 void xen_smp_intr_free_pv(unsigned int cpu) 100 { 101 kfree(per_cpu(xen_irq_work, cpu).name); 102 per_cpu(xen_irq_work, cpu).name = NULL; 103 if (per_cpu(xen_irq_work, cpu).irq >= 0) { 104 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL); 105 per_cpu(xen_irq_work, cpu).irq = -1; 106 } 107 108 kfree(per_cpu(xen_pmu_irq, cpu).name); 109 per_cpu(xen_pmu_irq, cpu).name = NULL; 110 if (per_cpu(xen_pmu_irq, cpu).irq >= 0) { 111 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL); 112 per_cpu(xen_pmu_irq, cpu).irq = -1; 113 } 114 } 115 116 int xen_smp_intr_init_pv(unsigned int cpu) 117 { 118 int rc; 119 char *callfunc_name, *pmu_name; 120 121 callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu); 122 per_cpu(xen_irq_work, cpu).name = callfunc_name; 123 rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR, 124 cpu, 125 xen_irq_work_interrupt, 126 IRQF_PERCPU|IRQF_NOBALANCING, 127 callfunc_name, 128 NULL); 129 if (rc < 0) 130 goto fail; 131 per_cpu(xen_irq_work, cpu).irq = rc; 132 133 if (is_xen_pmu) { 134 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu); 135 per_cpu(xen_pmu_irq, cpu).name = pmu_name; 136 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu, 137 xen_pmu_irq_handler, 138 IRQF_PERCPU|IRQF_NOBALANCING, 139 pmu_name, NULL); 140 if (rc < 0) 141 goto fail; 142 per_cpu(xen_pmu_irq, cpu).irq = rc; 143 } 144 145 return 0; 146 147 fail: 148 xen_smp_intr_free_pv(cpu); 149 return rc; 150 } 151 152 static void __init xen_pv_smp_config(void) 153 { 154 u32 apicid = 0; 155 int i; 156 157 topology_register_boot_apic(apicid++); 158 159 for (i = 1; i < nr_cpu_ids; i++) 160 topology_register_apic(apicid++, CPU_ACPIID_INVALID, true); 161 162 /* Pretend to be a proper enumerated system */ 163 smp_found_config = 1; 164 } 165 166 static void __init xen_pv_smp_prepare_boot_cpu(void) 167 { 168 BUG_ON(smp_processor_id() != 0); 169 native_smp_prepare_boot_cpu(); 170 171 if (!xen_feature(XENFEAT_writable_page_tables)) 172 /* We've switched to the "real" per-cpu gdt, so make 173 * sure the old memory can be recycled. */ 174 make_lowmem_page_readwrite(xen_initial_gdt); 175 176 xen_setup_vcpu_info_placement(); 177 178 /* 179 * The alternative logic (which patches the unlock/lock) runs before 180 * the smp bootup up code is activated. Hence we need to set this up 181 * the core kernel is being patched. Otherwise we will have only 182 * modules patched but not core code. 183 */ 184 xen_init_spinlocks(); 185 } 186 187 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus) 188 { 189 unsigned cpu; 190 191 if (ioapic_is_disabled) { 192 char *m = (max_cpus == 0) ? 193 "The nosmp parameter is incompatible with Xen; " \ 194 "use Xen dom0_max_vcpus=1 parameter" : 195 "The noapic parameter is incompatible with Xen"; 196 197 xen_raw_printk(m); 198 panic(m); 199 } 200 xen_init_lock_cpu(0); 201 202 smp_prepare_cpus_common(); 203 204 speculative_store_bypass_ht_init(); 205 206 xen_pmu_init(0); 207 208 if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0)) 209 BUG(); 210 211 if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL)) 212 panic("could not allocate xen_cpu_initialized_map\n"); 213 214 cpumask_copy(xen_cpu_initialized_map, cpumask_of(0)); 215 216 /* Restrict the possible_map according to max_cpus. */ 217 while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) { 218 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--) 219 continue; 220 set_cpu_possible(cpu, false); 221 } 222 223 for_each_possible_cpu(cpu) 224 set_cpu_present(cpu, true); 225 } 226 227 static int 228 cpu_initialize_context(unsigned int cpu, struct task_struct *idle) 229 { 230 struct vcpu_guest_context *ctxt; 231 struct desc_struct *gdt; 232 unsigned long gdt_mfn; 233 234 if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map)) 235 return 0; 236 237 ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL); 238 if (ctxt == NULL) { 239 cpumask_clear_cpu(cpu, xen_cpu_initialized_map); 240 return -ENOMEM; 241 } 242 243 gdt = get_cpu_gdt_rw(cpu); 244 245 /* 246 * Bring up the CPU in cpu_bringup_and_idle() with the stack 247 * pointing just below where pt_regs would be if it were a normal 248 * kernel entry. 249 */ 250 ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle; 251 ctxt->flags = VGCF_IN_KERNEL; 252 ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */ 253 ctxt->user_regs.ds = __USER_DS; 254 ctxt->user_regs.es = __USER_DS; 255 ctxt->user_regs.ss = __KERNEL_DS; 256 ctxt->user_regs.cs = __KERNEL_CS; 257 ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle); 258 259 xen_copy_trap_info(ctxt->trap_ctxt); 260 261 BUG_ON((unsigned long)gdt & ~PAGE_MASK); 262 263 gdt_mfn = arbitrary_virt_to_mfn(gdt); 264 make_lowmem_page_readonly(gdt); 265 make_lowmem_page_readonly(mfn_to_virt(gdt_mfn)); 266 267 ctxt->gdt_frames[0] = gdt_mfn; 268 ctxt->gdt_ents = GDT_ENTRIES; 269 270 /* 271 * Set SS:SP that Xen will use when entering guest kernel mode 272 * from guest user mode. Subsequent calls to load_sp0() can 273 * change this value. 274 */ 275 ctxt->kernel_ss = __KERNEL_DS; 276 ctxt->kernel_sp = task_top_of_stack(idle); 277 278 ctxt->gs_base_kernel = per_cpu_offset(cpu); 279 ctxt->event_callback_eip = 280 (unsigned long)xen_asm_exc_xen_hypervisor_callback; 281 ctxt->failsafe_callback_eip = 282 (unsigned long)xen_failsafe_callback; 283 per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir); 284 285 ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir)); 286 if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt)) 287 BUG(); 288 289 kfree(ctxt); 290 return 0; 291 } 292 293 static int xen_pv_kick_ap(unsigned int cpu, struct task_struct *idle) 294 { 295 int rc; 296 297 rc = common_cpu_up(cpu, idle); 298 if (rc) 299 return rc; 300 301 xen_setup_runstate_info(cpu); 302 303 /* make sure interrupts start blocked */ 304 per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1; 305 306 rc = cpu_initialize_context(cpu, idle); 307 if (rc) 308 return rc; 309 310 xen_pmu_init(cpu); 311 312 /* 313 * Why is this a BUG? If the hypercall fails then everything can be 314 * rolled back, no? 315 */ 316 BUG_ON(HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL)); 317 318 return 0; 319 } 320 321 static void xen_pv_poll_sync_state(void) 322 { 323 HYPERVISOR_sched_op(SCHEDOP_yield, NULL); 324 } 325 326 #ifdef CONFIG_HOTPLUG_CPU 327 static int xen_pv_cpu_disable(void) 328 { 329 unsigned int cpu = smp_processor_id(); 330 if (cpu == 0) 331 return -EBUSY; 332 333 cpu_disable_common(); 334 335 load_cr3(swapper_pg_dir); 336 return 0; 337 } 338 339 static void xen_pv_cpu_die(unsigned int cpu) 340 { 341 while (HYPERVISOR_vcpu_op(VCPUOP_is_up, xen_vcpu_nr(cpu), NULL)) { 342 __set_current_state(TASK_UNINTERRUPTIBLE); 343 schedule_timeout(HZ/10); 344 } 345 } 346 347 static void xen_pv_cleanup_dead_cpu(unsigned int cpu) 348 { 349 xen_smp_intr_free(cpu); 350 xen_uninit_lock_cpu(cpu); 351 xen_teardown_timer(cpu); 352 xen_pmu_finish(cpu); 353 } 354 355 static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */ 356 { 357 play_dead_common(); 358 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL); 359 xen_cpu_bringup_again((unsigned long)task_pt_regs(current)); 360 BUG(); 361 } 362 363 #else /* !CONFIG_HOTPLUG_CPU */ 364 static int xen_pv_cpu_disable(void) 365 { 366 return -ENOSYS; 367 } 368 369 static void xen_pv_cpu_die(unsigned int cpu) 370 { 371 BUG(); 372 } 373 374 static void xen_pv_cleanup_dead_cpu(unsigned int cpu) 375 { 376 BUG(); 377 } 378 379 static void __noreturn xen_pv_play_dead(void) 380 { 381 BUG(); 382 } 383 384 #endif 385 static void stop_self(void *v) 386 { 387 int cpu = smp_processor_id(); 388 389 /* make sure we're not pinning something down */ 390 load_cr3(swapper_pg_dir); 391 /* should set up a minimal gdt */ 392 393 set_cpu_online(cpu, false); 394 395 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL); 396 BUG(); 397 } 398 399 static void xen_pv_stop_other_cpus(int wait) 400 { 401 smp_call_function(stop_self, NULL, wait); 402 } 403 404 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id) 405 { 406 irq_work_run(); 407 inc_irq_stat(apic_irq_work_irqs); 408 409 return IRQ_HANDLED; 410 } 411 412 void __init xen_smp_count_cpus(void) 413 { 414 unsigned int cpus; 415 416 for (cpus = 0; cpus < nr_cpu_ids; cpus++) { 417 if (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpus, NULL) < 0) 418 break; 419 } 420 421 pr_info("Xen PV: Detected %u vCPUS\n", cpus); 422 if (cpus < nr_cpu_ids) 423 set_nr_cpu_ids(cpus); 424 } 425 426 static const struct smp_ops xen_smp_ops __initconst = { 427 .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu, 428 .smp_prepare_cpus = xen_pv_smp_prepare_cpus, 429 .smp_cpus_done = xen_smp_cpus_done, 430 431 .kick_ap_alive = xen_pv_kick_ap, 432 .cpu_die = xen_pv_cpu_die, 433 .cleanup_dead_cpu = xen_pv_cleanup_dead_cpu, 434 .poll_sync_state = xen_pv_poll_sync_state, 435 .cpu_disable = xen_pv_cpu_disable, 436 .play_dead = xen_pv_play_dead, 437 438 .stop_other_cpus = xen_pv_stop_other_cpus, 439 .smp_send_reschedule = xen_smp_send_reschedule, 440 441 .send_call_func_ipi = xen_smp_send_call_function_ipi, 442 .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi, 443 }; 444 445 void __init xen_smp_init(void) 446 { 447 smp_ops = xen_smp_ops; 448 449 /* Avoid searching for BIOS MP tables */ 450 x86_init.mpparse.find_mptable = x86_init_noop; 451 x86_init.mpparse.early_parse_smp_cfg = x86_init_noop; 452 453 /* XEN/PV Dom0 has halfways sane topology information via CPUID/MADT */ 454 if (xen_initial_domain()) 455 x86_init.mpparse.parse_smp_cfg = x86_init_noop; 456 else 457 x86_init.mpparse.parse_smp_cfg = xen_pv_smp_config; 458 } 459