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