1/*
 2 * Kernel-based Virtual Machine driver for Linux
 3 *
 4 * This module enables machines with Intel VT-x extensions to run virtual
 5 * machines without emulation or binary translation.
 6 *
 7 * timer support
 8 *
 9 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
10 *
11 * This work is licensed under the terms of the GNU GPL, version 2.  See
12 * the COPYING file in the top-level directory.
13 */
14
15#include <linux/kvm_host.h>
16#include <linux/kvm.h>
17#include <linux/hrtimer.h>
18#include <linux/atomic.h>
19#include "kvm_timer.h"
20
21static int __kvm_timer_fn(struct kvm_vcpu *vcpu, struct kvm_timer *ktimer)
22{
23	int restart_timer = 0;
24	wait_queue_head_t *q = &vcpu->wq;
25
26	/*
27	 * There is a race window between reading and incrementing, but we do
28	 * not care about potentially losing timer events in the !reinject
29	 * case anyway. Note: KVM_REQ_PENDING_TIMER is implicitly checked
30	 * in vcpu_enter_guest.
31	 */
32	if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
33		atomic_inc(&ktimer->pending);
34		/* FIXME: this code should not know anything about vcpus */
35		kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
36	}
37
38	if (waitqueue_active(q))
39		wake_up_interruptible(q);
40
41	if (ktimer->t_ops->is_periodic(ktimer)) {
42		hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
43		restart_timer = 1;
44	}
45
46	return restart_timer;
47}
48
49enum hrtimer_restart kvm_timer_fn(struct hrtimer *data)
50{
51	int restart_timer;
52	struct kvm_vcpu *vcpu;
53	struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
54
55	vcpu = ktimer->vcpu;
56	if (!vcpu)
57		return HRTIMER_NORESTART;
58
59	restart_timer = __kvm_timer_fn(vcpu, ktimer);
60	if (restart_timer)
61		return HRTIMER_RESTART;
62	else
63		return HRTIMER_NORESTART;
64}
65