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