1 /* 2 * KVM paravirt_ops implementation 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. 17 * 18 * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com> 19 * Copyright IBM Corporation, 2007 20 * Authors: Anthony Liguori <aliguori@us.ibm.com> 21 */ 22 23 #include <linux/context_tracking.h> 24 #include <linux/init.h> 25 #include <linux/kernel.h> 26 #include <linux/kvm_para.h> 27 #include <linux/cpu.h> 28 #include <linux/mm.h> 29 #include <linux/highmem.h> 30 #include <linux/hardirq.h> 31 #include <linux/notifier.h> 32 #include <linux/reboot.h> 33 #include <linux/hash.h> 34 #include <linux/sched.h> 35 #include <linux/slab.h> 36 #include <linux/kprobes.h> 37 #include <linux/debugfs.h> 38 #include <linux/nmi.h> 39 #include <linux/swait.h> 40 #include <asm/timer.h> 41 #include <asm/cpu.h> 42 #include <asm/traps.h> 43 #include <asm/desc.h> 44 #include <asm/tlbflush.h> 45 #include <asm/idle.h> 46 #include <asm/apic.h> 47 #include <asm/apicdef.h> 48 #include <asm/hypervisor.h> 49 #include <asm/kvm_guest.h> 50 51 static int kvmapf = 1; 52 53 static int parse_no_kvmapf(char *arg) 54 { 55 kvmapf = 0; 56 return 0; 57 } 58 59 early_param("no-kvmapf", parse_no_kvmapf); 60 61 static int steal_acc = 1; 62 static int parse_no_stealacc(char *arg) 63 { 64 steal_acc = 0; 65 return 0; 66 } 67 68 early_param("no-steal-acc", parse_no_stealacc); 69 70 static int kvmclock_vsyscall = 1; 71 static int parse_no_kvmclock_vsyscall(char *arg) 72 { 73 kvmclock_vsyscall = 0; 74 return 0; 75 } 76 77 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall); 78 79 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64); 80 static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64); 81 static int has_steal_clock = 0; 82 83 /* 84 * No need for any "IO delay" on KVM 85 */ 86 static void kvm_io_delay(void) 87 { 88 } 89 90 #define KVM_TASK_SLEEP_HASHBITS 8 91 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS) 92 93 struct kvm_task_sleep_node { 94 struct hlist_node link; 95 struct swait_queue_head wq; 96 u32 token; 97 int cpu; 98 bool halted; 99 }; 100 101 static struct kvm_task_sleep_head { 102 raw_spinlock_t lock; 103 struct hlist_head list; 104 } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE]; 105 106 static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b, 107 u32 token) 108 { 109 struct hlist_node *p; 110 111 hlist_for_each(p, &b->list) { 112 struct kvm_task_sleep_node *n = 113 hlist_entry(p, typeof(*n), link); 114 if (n->token == token) 115 return n; 116 } 117 118 return NULL; 119 } 120 121 void kvm_async_pf_task_wait(u32 token) 122 { 123 u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS); 124 struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; 125 struct kvm_task_sleep_node n, *e; 126 DECLARE_SWAITQUEUE(wait); 127 128 rcu_irq_enter(); 129 130 raw_spin_lock(&b->lock); 131 e = _find_apf_task(b, token); 132 if (e) { 133 /* dummy entry exist -> wake up was delivered ahead of PF */ 134 hlist_del(&e->link); 135 kfree(e); 136 raw_spin_unlock(&b->lock); 137 138 rcu_irq_exit(); 139 return; 140 } 141 142 n.token = token; 143 n.cpu = smp_processor_id(); 144 n.halted = is_idle_task(current) || preempt_count() > 1; 145 init_swait_queue_head(&n.wq); 146 hlist_add_head(&n.link, &b->list); 147 raw_spin_unlock(&b->lock); 148 149 for (;;) { 150 if (!n.halted) 151 prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); 152 if (hlist_unhashed(&n.link)) 153 break; 154 155 if (!n.halted) { 156 local_irq_enable(); 157 schedule(); 158 local_irq_disable(); 159 } else { 160 /* 161 * We cannot reschedule. So halt. 162 */ 163 rcu_irq_exit(); 164 native_safe_halt(); 165 rcu_irq_enter(); 166 local_irq_disable(); 167 } 168 } 169 if (!n.halted) 170 finish_swait(&n.wq, &wait); 171 172 rcu_irq_exit(); 173 return; 174 } 175 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait); 176 177 static void apf_task_wake_one(struct kvm_task_sleep_node *n) 178 { 179 hlist_del_init(&n->link); 180 if (n->halted) 181 smp_send_reschedule(n->cpu); 182 else if (swait_active(&n->wq)) 183 swake_up(&n->wq); 184 } 185 186 static void apf_task_wake_all(void) 187 { 188 int i; 189 190 for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) { 191 struct hlist_node *p, *next; 192 struct kvm_task_sleep_head *b = &async_pf_sleepers[i]; 193 raw_spin_lock(&b->lock); 194 hlist_for_each_safe(p, next, &b->list) { 195 struct kvm_task_sleep_node *n = 196 hlist_entry(p, typeof(*n), link); 197 if (n->cpu == smp_processor_id()) 198 apf_task_wake_one(n); 199 } 200 raw_spin_unlock(&b->lock); 201 } 202 } 203 204 void kvm_async_pf_task_wake(u32 token) 205 { 206 u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS); 207 struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; 208 struct kvm_task_sleep_node *n; 209 210 if (token == ~0) { 211 apf_task_wake_all(); 212 return; 213 } 214 215 again: 216 raw_spin_lock(&b->lock); 217 n = _find_apf_task(b, token); 218 if (!n) { 219 /* 220 * async PF was not yet handled. 221 * Add dummy entry for the token. 222 */ 223 n = kzalloc(sizeof(*n), GFP_ATOMIC); 224 if (!n) { 225 /* 226 * Allocation failed! Busy wait while other cpu 227 * handles async PF. 228 */ 229 raw_spin_unlock(&b->lock); 230 cpu_relax(); 231 goto again; 232 } 233 n->token = token; 234 n->cpu = smp_processor_id(); 235 init_swait_queue_head(&n->wq); 236 hlist_add_head(&n->link, &b->list); 237 } else 238 apf_task_wake_one(n); 239 raw_spin_unlock(&b->lock); 240 return; 241 } 242 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake); 243 244 u32 kvm_read_and_reset_pf_reason(void) 245 { 246 u32 reason = 0; 247 248 if (__this_cpu_read(apf_reason.enabled)) { 249 reason = __this_cpu_read(apf_reason.reason); 250 __this_cpu_write(apf_reason.reason, 0); 251 } 252 253 return reason; 254 } 255 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason); 256 NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason); 257 258 dotraplinkage void 259 do_async_page_fault(struct pt_regs *regs, unsigned long error_code) 260 { 261 enum ctx_state prev_state; 262 263 switch (kvm_read_and_reset_pf_reason()) { 264 default: 265 trace_do_page_fault(regs, error_code); 266 break; 267 case KVM_PV_REASON_PAGE_NOT_PRESENT: 268 /* page is swapped out by the host. */ 269 prev_state = exception_enter(); 270 exit_idle(); 271 kvm_async_pf_task_wait((u32)read_cr2()); 272 exception_exit(prev_state); 273 break; 274 case KVM_PV_REASON_PAGE_READY: 275 rcu_irq_enter(); 276 exit_idle(); 277 kvm_async_pf_task_wake((u32)read_cr2()); 278 rcu_irq_exit(); 279 break; 280 } 281 } 282 NOKPROBE_SYMBOL(do_async_page_fault); 283 284 static void __init paravirt_ops_setup(void) 285 { 286 pv_info.name = "KVM"; 287 288 if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY)) 289 pv_cpu_ops.io_delay = kvm_io_delay; 290 291 #ifdef CONFIG_X86_IO_APIC 292 no_timer_check = 1; 293 #endif 294 } 295 296 static void kvm_register_steal_time(void) 297 { 298 int cpu = smp_processor_id(); 299 struct kvm_steal_time *st = &per_cpu(steal_time, cpu); 300 301 if (!has_steal_clock) 302 return; 303 304 wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED)); 305 pr_info("kvm-stealtime: cpu %d, msr %llx\n", 306 cpu, (unsigned long long) slow_virt_to_phys(st)); 307 } 308 309 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED; 310 311 static void kvm_guest_apic_eoi_write(u32 reg, u32 val) 312 { 313 /** 314 * This relies on __test_and_clear_bit to modify the memory 315 * in a way that is atomic with respect to the local CPU. 316 * The hypervisor only accesses this memory from the local CPU so 317 * there's no need for lock or memory barriers. 318 * An optimization barrier is implied in apic write. 319 */ 320 if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi))) 321 return; 322 apic_write(APIC_EOI, APIC_EOI_ACK); 323 } 324 325 static void kvm_guest_cpu_init(void) 326 { 327 if (!kvm_para_available()) 328 return; 329 330 if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) { 331 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason)); 332 333 #ifdef CONFIG_PREEMPT 334 pa |= KVM_ASYNC_PF_SEND_ALWAYS; 335 #endif 336 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED); 337 __this_cpu_write(apf_reason.enabled, 1); 338 printk(KERN_INFO"KVM setup async PF for cpu %d\n", 339 smp_processor_id()); 340 } 341 342 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) { 343 unsigned long pa; 344 /* Size alignment is implied but just to make it explicit. */ 345 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4); 346 __this_cpu_write(kvm_apic_eoi, 0); 347 pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi)) 348 | KVM_MSR_ENABLED; 349 wrmsrl(MSR_KVM_PV_EOI_EN, pa); 350 } 351 352 if (has_steal_clock) 353 kvm_register_steal_time(); 354 } 355 356 static void kvm_pv_disable_apf(void) 357 { 358 if (!__this_cpu_read(apf_reason.enabled)) 359 return; 360 361 wrmsrl(MSR_KVM_ASYNC_PF_EN, 0); 362 __this_cpu_write(apf_reason.enabled, 0); 363 364 printk(KERN_INFO"Unregister pv shared memory for cpu %d\n", 365 smp_processor_id()); 366 } 367 368 static void kvm_pv_guest_cpu_reboot(void *unused) 369 { 370 /* 371 * We disable PV EOI before we load a new kernel by kexec, 372 * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory. 373 * New kernel can re-enable when it boots. 374 */ 375 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) 376 wrmsrl(MSR_KVM_PV_EOI_EN, 0); 377 kvm_pv_disable_apf(); 378 kvm_disable_steal_time(); 379 } 380 381 static int kvm_pv_reboot_notify(struct notifier_block *nb, 382 unsigned long code, void *unused) 383 { 384 if (code == SYS_RESTART) 385 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1); 386 return NOTIFY_DONE; 387 } 388 389 static struct notifier_block kvm_pv_reboot_nb = { 390 .notifier_call = kvm_pv_reboot_notify, 391 }; 392 393 static u64 kvm_steal_clock(int cpu) 394 { 395 u64 steal; 396 struct kvm_steal_time *src; 397 int version; 398 399 src = &per_cpu(steal_time, cpu); 400 do { 401 version = src->version; 402 rmb(); 403 steal = src->steal; 404 rmb(); 405 } while ((version & 1) || (version != src->version)); 406 407 return steal; 408 } 409 410 void kvm_disable_steal_time(void) 411 { 412 if (!has_steal_clock) 413 return; 414 415 wrmsr(MSR_KVM_STEAL_TIME, 0, 0); 416 } 417 418 #ifdef CONFIG_SMP 419 static void __init kvm_smp_prepare_boot_cpu(void) 420 { 421 kvm_guest_cpu_init(); 422 native_smp_prepare_boot_cpu(); 423 kvm_spinlock_init(); 424 } 425 426 static void kvm_guest_cpu_offline(void) 427 { 428 kvm_disable_steal_time(); 429 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) 430 wrmsrl(MSR_KVM_PV_EOI_EN, 0); 431 kvm_pv_disable_apf(); 432 apf_task_wake_all(); 433 } 434 435 static int kvm_cpu_online(unsigned int cpu) 436 { 437 local_irq_disable(); 438 kvm_guest_cpu_init(); 439 local_irq_enable(); 440 return 0; 441 } 442 443 static int kvm_cpu_down_prepare(unsigned int cpu) 444 { 445 local_irq_disable(); 446 kvm_guest_cpu_offline(); 447 local_irq_enable(); 448 return 0; 449 } 450 #endif 451 452 static void __init kvm_apf_trap_init(void) 453 { 454 set_intr_gate(14, async_page_fault); 455 } 456 457 void __init kvm_guest_init(void) 458 { 459 int i; 460 461 if (!kvm_para_available()) 462 return; 463 464 paravirt_ops_setup(); 465 register_reboot_notifier(&kvm_pv_reboot_nb); 466 for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) 467 raw_spin_lock_init(&async_pf_sleepers[i].lock); 468 if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF)) 469 x86_init.irqs.trap_init = kvm_apf_trap_init; 470 471 if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { 472 has_steal_clock = 1; 473 pv_time_ops.steal_clock = kvm_steal_clock; 474 } 475 476 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) 477 apic_set_eoi_write(kvm_guest_apic_eoi_write); 478 479 if (kvmclock_vsyscall) 480 kvm_setup_vsyscall_timeinfo(); 481 482 #ifdef CONFIG_SMP 483 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; 484 if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online", 485 kvm_cpu_online, kvm_cpu_down_prepare) < 0) 486 pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n"); 487 #else 488 kvm_guest_cpu_init(); 489 #endif 490 491 /* 492 * Hard lockup detection is enabled by default. Disable it, as guests 493 * can get false positives too easily, for example if the host is 494 * overcommitted. 495 */ 496 hardlockup_detector_disable(); 497 } 498 499 static noinline uint32_t __kvm_cpuid_base(void) 500 { 501 if (boot_cpu_data.cpuid_level < 0) 502 return 0; /* So we don't blow up on old processors */ 503 504 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) 505 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0); 506 507 return 0; 508 } 509 510 static inline uint32_t kvm_cpuid_base(void) 511 { 512 static int kvm_cpuid_base = -1; 513 514 if (kvm_cpuid_base == -1) 515 kvm_cpuid_base = __kvm_cpuid_base(); 516 517 return kvm_cpuid_base; 518 } 519 520 bool kvm_para_available(void) 521 { 522 return kvm_cpuid_base() != 0; 523 } 524 EXPORT_SYMBOL_GPL(kvm_para_available); 525 526 unsigned int kvm_arch_para_features(void) 527 { 528 return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES); 529 } 530 531 static uint32_t __init kvm_detect(void) 532 { 533 return kvm_cpuid_base(); 534 } 535 536 const struct hypervisor_x86 x86_hyper_kvm __refconst = { 537 .name = "KVM", 538 .detect = kvm_detect, 539 .x2apic_available = kvm_para_available, 540 }; 541 EXPORT_SYMBOL_GPL(x86_hyper_kvm); 542 543 static __init int activate_jump_labels(void) 544 { 545 if (has_steal_clock) { 546 static_key_slow_inc(¶virt_steal_enabled); 547 if (steal_acc) 548 static_key_slow_inc(¶virt_steal_rq_enabled); 549 } 550 551 return 0; 552 } 553 arch_initcall(activate_jump_labels); 554 555 #ifdef CONFIG_PARAVIRT_SPINLOCKS 556 557 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */ 558 static void kvm_kick_cpu(int cpu) 559 { 560 int apicid; 561 unsigned long flags = 0; 562 563 apicid = per_cpu(x86_cpu_to_apicid, cpu); 564 kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid); 565 } 566 567 #include <asm/qspinlock.h> 568 569 static void kvm_wait(u8 *ptr, u8 val) 570 { 571 unsigned long flags; 572 573 if (in_nmi()) 574 return; 575 576 local_irq_save(flags); 577 578 if (READ_ONCE(*ptr) != val) 579 goto out; 580 581 /* 582 * halt until it's our turn and kicked. Note that we do safe halt 583 * for irq enabled case to avoid hang when lock info is overwritten 584 * in irq spinlock slowpath and no spurious interrupt occur to save us. 585 */ 586 if (arch_irqs_disabled_flags(flags)) 587 halt(); 588 else 589 safe_halt(); 590 591 out: 592 local_irq_restore(flags); 593 } 594 595 /* 596 * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. 597 */ 598 void __init kvm_spinlock_init(void) 599 { 600 if (!kvm_para_available()) 601 return; 602 /* Does host kernel support KVM_FEATURE_PV_UNHALT? */ 603 if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) 604 return; 605 606 __pv_init_lock_hash(); 607 pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath; 608 pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock); 609 pv_lock_ops.wait = kvm_wait; 610 pv_lock_ops.kick = kvm_kick_cpu; 611 } 612 613 static __init int kvm_spinlock_init_jump(void) 614 { 615 if (!kvm_para_available()) 616 return 0; 617 if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) 618 return 0; 619 620 static_key_slow_inc(¶virt_ticketlocks_enabled); 621 printk(KERN_INFO "KVM setup paravirtual spinlock\n"); 622 623 return 0; 624 } 625 early_initcall(kvm_spinlock_init_jump); 626 627 #endif /* CONFIG_PARAVIRT_SPINLOCKS */ 628