2 * KVM paravirt_ops implementation
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.
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.
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.
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>
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>
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>
42 #include <asm/traps.h>
44 #include <asm/tlbflush.h>
46 #include <asm/apicdef.h>
47 #include <asm/hypervisor.h>
48 #include <asm/kvm_guest.h>
50 static int kvmapf
= 1;
52 static int parse_no_kvmapf(char *arg
)
58 early_param("no-kvmapf", parse_no_kvmapf
);
60 static int steal_acc
= 1;
61 static int parse_no_stealacc(char *arg
)
67 early_param("no-steal-acc", parse_no_stealacc
);
69 static int kvmclock_vsyscall
= 1;
70 static int parse_no_kvmclock_vsyscall(char *arg
)
72 kvmclock_vsyscall
= 0;
76 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall
);
78 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data
, apf_reason
) __aligned(64);
79 static DEFINE_PER_CPU(struct kvm_steal_time
, steal_time
) __aligned(64);
80 static int has_steal_clock
= 0;
83 * No need for any "IO delay" on KVM
85 static void kvm_io_delay(void)
89 #define KVM_TASK_SLEEP_HASHBITS 8
90 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
92 struct kvm_task_sleep_node
{
93 struct hlist_node link
;
94 struct swait_queue_head wq
;
100 static struct kvm_task_sleep_head
{
102 struct hlist_head list
;
103 } async_pf_sleepers
[KVM_TASK_SLEEP_HASHSIZE
];
105 static struct kvm_task_sleep_node
*_find_apf_task(struct kvm_task_sleep_head
*b
,
108 struct hlist_node
*p
;
110 hlist_for_each(p
, &b
->list
) {
111 struct kvm_task_sleep_node
*n
=
112 hlist_entry(p
, typeof(*n
), link
);
113 if (n
->token
== token
)
120 void kvm_async_pf_task_wait(u32 token
)
122 u32 key
= hash_32(token
, KVM_TASK_SLEEP_HASHBITS
);
123 struct kvm_task_sleep_head
*b
= &async_pf_sleepers
[key
];
124 struct kvm_task_sleep_node n
, *e
;
125 DECLARE_SWAITQUEUE(wait
);
129 raw_spin_lock(&b
->lock
);
130 e
= _find_apf_task(b
, token
);
132 /* dummy entry exist -> wake up was delivered ahead of PF */
135 raw_spin_unlock(&b
->lock
);
142 n
.cpu
= smp_processor_id();
143 n
.halted
= is_idle_task(current
) || preempt_count() > 1;
144 init_swait_queue_head(&n
.wq
);
145 hlist_add_head(&n
.link
, &b
->list
);
146 raw_spin_unlock(&b
->lock
);
150 prepare_to_swait(&n
.wq
, &wait
, TASK_UNINTERRUPTIBLE
);
151 if (hlist_unhashed(&n
.link
))
162 * We cannot reschedule. So halt.
171 finish_swait(&n
.wq
, &wait
);
176 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait
);
178 static void apf_task_wake_one(struct kvm_task_sleep_node
*n
)
180 hlist_del_init(&n
->link
);
182 smp_send_reschedule(n
->cpu
);
183 else if (swait_active(&n
->wq
))
187 static void apf_task_wake_all(void)
191 for (i
= 0; i
< KVM_TASK_SLEEP_HASHSIZE
; i
++) {
192 struct hlist_node
*p
, *next
;
193 struct kvm_task_sleep_head
*b
= &async_pf_sleepers
[i
];
194 raw_spin_lock(&b
->lock
);
195 hlist_for_each_safe(p
, next
, &b
->list
) {
196 struct kvm_task_sleep_node
*n
=
197 hlist_entry(p
, typeof(*n
), link
);
198 if (n
->cpu
== smp_processor_id())
199 apf_task_wake_one(n
);
201 raw_spin_unlock(&b
->lock
);
205 void kvm_async_pf_task_wake(u32 token
)
207 u32 key
= hash_32(token
, KVM_TASK_SLEEP_HASHBITS
);
208 struct kvm_task_sleep_head
*b
= &async_pf_sleepers
[key
];
209 struct kvm_task_sleep_node
*n
;
217 raw_spin_lock(&b
->lock
);
218 n
= _find_apf_task(b
, token
);
221 * async PF was not yet handled.
222 * Add dummy entry for the token.
224 n
= kzalloc(sizeof(*n
), GFP_ATOMIC
);
227 * Allocation failed! Busy wait while other cpu
230 raw_spin_unlock(&b
->lock
);
235 n
->cpu
= smp_processor_id();
236 init_swait_queue_head(&n
->wq
);
237 hlist_add_head(&n
->link
, &b
->list
);
239 apf_task_wake_one(n
);
240 raw_spin_unlock(&b
->lock
);
243 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake
);
245 u32
kvm_read_and_reset_pf_reason(void)
249 if (__this_cpu_read(apf_reason
.enabled
)) {
250 reason
= __this_cpu_read(apf_reason
.reason
);
251 __this_cpu_write(apf_reason
.reason
, 0);
256 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason
);
257 NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason
);
260 do_async_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
262 enum ctx_state prev_state
;
264 switch (kvm_read_and_reset_pf_reason()) {
266 trace_do_page_fault(regs
, error_code
);
268 case KVM_PV_REASON_PAGE_NOT_PRESENT
:
269 /* page is swapped out by the host. */
270 prev_state
= exception_enter();
271 kvm_async_pf_task_wait((u32
)read_cr2());
272 exception_exit(prev_state
);
274 case KVM_PV_REASON_PAGE_READY
:
276 kvm_async_pf_task_wake((u32
)read_cr2());
281 NOKPROBE_SYMBOL(do_async_page_fault
);
283 static void __init
paravirt_ops_setup(void)
285 pv_info
.name
= "KVM";
287 if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY
))
288 pv_cpu_ops
.io_delay
= kvm_io_delay
;
290 #ifdef CONFIG_X86_IO_APIC
295 static void kvm_register_steal_time(void)
297 int cpu
= smp_processor_id();
298 struct kvm_steal_time
*st
= &per_cpu(steal_time
, cpu
);
300 if (!has_steal_clock
)
303 wrmsrl(MSR_KVM_STEAL_TIME
, (slow_virt_to_phys(st
) | KVM_MSR_ENABLED
));
304 pr_info("kvm-stealtime: cpu %d, msr %llx\n",
305 cpu
, (unsigned long long) slow_virt_to_phys(st
));
308 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi
) = KVM_PV_EOI_DISABLED
;
310 static notrace
void kvm_guest_apic_eoi_write(u32 reg
, u32 val
)
313 * This relies on __test_and_clear_bit to modify the memory
314 * in a way that is atomic with respect to the local CPU.
315 * The hypervisor only accesses this memory from the local CPU so
316 * there's no need for lock or memory barriers.
317 * An optimization barrier is implied in apic write.
319 if (__test_and_clear_bit(KVM_PV_EOI_BIT
, this_cpu_ptr(&kvm_apic_eoi
)))
321 apic
->native_eoi_write(APIC_EOI
, APIC_EOI_ACK
);
324 static void kvm_guest_cpu_init(void)
326 if (!kvm_para_available())
329 if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF
) && kvmapf
) {
330 u64 pa
= slow_virt_to_phys(this_cpu_ptr(&apf_reason
));
332 #ifdef CONFIG_PREEMPT
333 pa
|= KVM_ASYNC_PF_SEND_ALWAYS
;
335 pa
|= KVM_ASYNC_PF_ENABLED
;
337 /* Async page fault support for L1 hypervisor is optional */
338 if (wrmsr_safe(MSR_KVM_ASYNC_PF_EN
,
339 (pa
| KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT
) & 0xffffffff, pa
>> 32) < 0)
340 wrmsrl(MSR_KVM_ASYNC_PF_EN
, pa
);
341 __this_cpu_write(apf_reason
.enabled
, 1);
342 printk(KERN_INFO
"KVM setup async PF for cpu %d\n",
346 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI
)) {
348 /* Size alignment is implied but just to make it explicit. */
349 BUILD_BUG_ON(__alignof__(kvm_apic_eoi
) < 4);
350 __this_cpu_write(kvm_apic_eoi
, 0);
351 pa
= slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi
))
353 wrmsrl(MSR_KVM_PV_EOI_EN
, pa
);
357 kvm_register_steal_time();
360 static void kvm_pv_disable_apf(void)
362 if (!__this_cpu_read(apf_reason
.enabled
))
365 wrmsrl(MSR_KVM_ASYNC_PF_EN
, 0);
366 __this_cpu_write(apf_reason
.enabled
, 0);
368 printk(KERN_INFO
"Unregister pv shared memory for cpu %d\n",
372 static void kvm_pv_guest_cpu_reboot(void *unused
)
375 * We disable PV EOI before we load a new kernel by kexec,
376 * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
377 * New kernel can re-enable when it boots.
379 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI
))
380 wrmsrl(MSR_KVM_PV_EOI_EN
, 0);
381 kvm_pv_disable_apf();
382 kvm_disable_steal_time();
385 static int kvm_pv_reboot_notify(struct notifier_block
*nb
,
386 unsigned long code
, void *unused
)
388 if (code
== SYS_RESTART
)
389 on_each_cpu(kvm_pv_guest_cpu_reboot
, NULL
, 1);
393 static struct notifier_block kvm_pv_reboot_nb
= {
394 .notifier_call
= kvm_pv_reboot_notify
,
397 static u64
kvm_steal_clock(int cpu
)
400 struct kvm_steal_time
*src
;
403 src
= &per_cpu(steal_time
, cpu
);
405 version
= src
->version
;
409 } while ((version
& 1) || (version
!= src
->version
));
414 void kvm_disable_steal_time(void)
416 if (!has_steal_clock
)
419 wrmsr(MSR_KVM_STEAL_TIME
, 0, 0);
423 static void __init
kvm_smp_prepare_boot_cpu(void)
425 kvm_guest_cpu_init();
426 native_smp_prepare_boot_cpu();
430 static void kvm_guest_cpu_offline(void)
432 kvm_disable_steal_time();
433 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI
))
434 wrmsrl(MSR_KVM_PV_EOI_EN
, 0);
435 kvm_pv_disable_apf();
439 static int kvm_cpu_online(unsigned int cpu
)
442 kvm_guest_cpu_init();
447 static int kvm_cpu_down_prepare(unsigned int cpu
)
450 kvm_guest_cpu_offline();
456 static void __init
kvm_apf_trap_init(void)
458 set_intr_gate(14, async_page_fault
);
461 void __init
kvm_guest_init(void)
465 if (!kvm_para_available())
468 paravirt_ops_setup();
469 register_reboot_notifier(&kvm_pv_reboot_nb
);
470 for (i
= 0; i
< KVM_TASK_SLEEP_HASHSIZE
; i
++)
471 raw_spin_lock_init(&async_pf_sleepers
[i
].lock
);
472 if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF
))
473 x86_init
.irqs
.trap_init
= kvm_apf_trap_init
;
475 if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME
)) {
477 pv_time_ops
.steal_clock
= kvm_steal_clock
;
480 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI
))
481 apic_set_eoi_write(kvm_guest_apic_eoi_write
);
483 if (kvmclock_vsyscall
)
484 kvm_setup_vsyscall_timeinfo();
487 smp_ops
.smp_prepare_boot_cpu
= kvm_smp_prepare_boot_cpu
;
488 if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
, "x86/kvm:online",
489 kvm_cpu_online
, kvm_cpu_down_prepare
) < 0)
490 pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
492 kvm_guest_cpu_init();
496 * Hard lockup detection is enabled by default. Disable it, as guests
497 * can get false positives too easily, for example if the host is
500 hardlockup_detector_disable();
503 static noinline
uint32_t __kvm_cpuid_base(void)
505 if (boot_cpu_data
.cpuid_level
< 0)
506 return 0; /* So we don't blow up on old processors */
508 if (boot_cpu_has(X86_FEATURE_HYPERVISOR
))
509 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
514 static inline uint32_t kvm_cpuid_base(void)
516 static int kvm_cpuid_base
= -1;
518 if (kvm_cpuid_base
== -1)
519 kvm_cpuid_base
= __kvm_cpuid_base();
521 return kvm_cpuid_base
;
524 bool kvm_para_available(void)
526 return kvm_cpuid_base() != 0;
528 EXPORT_SYMBOL_GPL(kvm_para_available
);
530 unsigned int kvm_arch_para_features(void)
532 return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES
);
535 static uint32_t __init
kvm_detect(void)
537 return kvm_cpuid_base();
540 const struct hypervisor_x86 x86_hyper_kvm __refconst
= {
542 .detect
= kvm_detect
,
543 .x2apic_available
= kvm_para_available
,
545 EXPORT_SYMBOL_GPL(x86_hyper_kvm
);
547 static __init
int activate_jump_labels(void)
549 if (has_steal_clock
) {
550 static_key_slow_inc(¶virt_steal_enabled
);
552 static_key_slow_inc(¶virt_steal_rq_enabled
);
557 arch_initcall(activate_jump_labels
);
559 #ifdef CONFIG_PARAVIRT_SPINLOCKS
561 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
562 static void kvm_kick_cpu(int cpu
)
565 unsigned long flags
= 0;
567 apicid
= per_cpu(x86_cpu_to_apicid
, cpu
);
568 kvm_hypercall2(KVM_HC_KICK_CPU
, flags
, apicid
);
571 #include <asm/qspinlock.h>
573 static void kvm_wait(u8
*ptr
, u8 val
)
580 local_irq_save(flags
);
582 if (READ_ONCE(*ptr
) != val
)
586 * halt until it's our turn and kicked. Note that we do safe halt
587 * for irq enabled case to avoid hang when lock info is overwritten
588 * in irq spinlock slowpath and no spurious interrupt occur to save us.
590 if (arch_irqs_disabled_flags(flags
))
596 local_irq_restore(flags
);
600 __visible
bool __kvm_vcpu_is_preempted(long cpu
)
602 struct kvm_steal_time
*src
= &per_cpu(steal_time
, cpu
);
604 return !!src
->preempted
;
606 PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted
);
610 #include <asm/asm-offsets.h>
612 extern bool __raw_callee_save___kvm_vcpu_is_preempted(long);
615 * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and
616 * restoring to/from the stack.
619 ".pushsection .text;"
620 ".global __raw_callee_save___kvm_vcpu_is_preempted;"
621 ".type __raw_callee_save___kvm_vcpu_is_preempted, @function;"
622 "__raw_callee_save___kvm_vcpu_is_preempted:"
623 "movq __per_cpu_offset(,%rdi,8), %rax;"
624 "cmpb $0, " __stringify(KVM_STEAL_TIME_preempted
) "+steal_time(%rax);"
632 * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
634 void __init
kvm_spinlock_init(void)
636 if (!kvm_para_available())
638 /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
639 if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT
))
642 __pv_init_lock_hash();
643 pv_lock_ops
.queued_spin_lock_slowpath
= __pv_queued_spin_lock_slowpath
;
644 pv_lock_ops
.queued_spin_unlock
= PV_CALLEE_SAVE(__pv_queued_spin_unlock
);
645 pv_lock_ops
.wait
= kvm_wait
;
646 pv_lock_ops
.kick
= kvm_kick_cpu
;
648 if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME
)) {
649 pv_lock_ops
.vcpu_is_preempted
=
650 PV_CALLEE_SAVE(__kvm_vcpu_is_preempted
);
654 #endif /* CONFIG_PARAVIRT_SPINLOCKS */