arch/x86/kvm/timer.c

   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
  21 enum hrtimer_restart kvm_timer_fn(struct hrtimer *data)
  22 {
  23         struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
  24         struct kvm_vcpu *vcpu = ktimer->vcpu;
  25         wait_queue_head_t *q = &vcpu->wq;
  26
  27         /*
  28          * There is a race window between reading and incrementing, but we do
  29          * not care about potentially losing timer events in the !reinject
  30          * case anyway. Note: KVM_REQ_PENDING_TIMER is implicitly checked
  31          * in vcpu_enter_guest.
  32          */
  33         if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
  34                 atomic_inc(&ktimer->pending);
  35                 /* FIXME: this code should not know anything about vcpus */
  36                 kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
  37         }
  38
  39         if (waitqueue_active(q))
  40                 wake_up_interruptible(q);
  41
  42         if (ktimer->t_ops->is_periodic(ktimer)) {
  43                 hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
  44                 return HRTIMER_RESTART;
  45         } else
  46                 return HRTIMER_NORESTART;
  47 }