KVM: x86: document KVM_REQ_PENDING_TIMER usage
[linux-3.10.git] / arch / x86 / kvm / timer.c
1 #include <linux/kvm_host.h>
2 #include <linux/kvm.h>
3 #include <linux/hrtimer.h>
4 #include <asm/atomic.h>
5 #include "kvm_timer.h"
6
7 static int __kvm_timer_fn(struct kvm_vcpu *vcpu, struct kvm_timer *ktimer)
8 {
9         int restart_timer = 0;
10         wait_queue_head_t *q = &vcpu->wq;
11
12         /*
13          * There is a race window between reading and incrementing, but we do
14          * not care about potentially loosing timer events in the !reinject
15          * case anyway. Note: KVM_REQ_PENDING_TIMER is implicitly checked
16          * in vcpu_enter_guest.
17          */
18         if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
19                 atomic_inc(&ktimer->pending);
20                 /* FIXME: this code should not know anything about vcpus */
21                 set_bit(KVM_REQ_PENDING_TIMER, &vcpu->requests);
22         }
23
24         if (waitqueue_active(q))
25                 wake_up_interruptible(q);
26
27         if (ktimer->t_ops->is_periodic(ktimer)) {
28                 hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
29                 restart_timer = 1;
30         }
31
32         return restart_timer;
33 }
34
35 enum hrtimer_restart kvm_timer_fn(struct hrtimer *data)
36 {
37         int restart_timer;
38         struct kvm_vcpu *vcpu;
39         struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
40
41         vcpu = ktimer->vcpu;
42         if (!vcpu)
43                 return HRTIMER_NORESTART;
44
45         restart_timer = __kvm_timer_fn(vcpu, ktimer);
46         if (restart_timer)
47                 return HRTIMER_RESTART;
48         else
49                 return HRTIMER_NORESTART;
50 }
51