release/src-rt-6.x.4708/linux/linux-2.6.36/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 affilates.
  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 <asm/atomic.h>
  19 #include "kvm_timer.h"
  20
  21 static 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 loosing 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                 kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
  35         }
  36
  37         if (waitqueue_active(q))
  38                 wake_up_interruptible(q);
  39
  40         if (ktimer->t_ops->is_periodic(ktimer)) {
  41                 hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
  42                 restart_timer = 1;
  43         }
  44
  45         return restart_timer;
  46 }
  47
  48 enum hrtimer_restart kvm_timer_fn(struct hrtimer *data)
  49 {
  50         int restart_timer;
  51         struct kvm_vcpu *vcpu;
  52         struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
  53
  54         vcpu = ktimer->vcpu;
  55         if (!vcpu)
  56                 return HRTIMER_NORESTART;
  57
  58         restart_timer = __kvm_timer_fn(vcpu, ktimer);
  59         if (restart_timer)
  60                 return HRTIMER_RESTART;
  61         else
  62                 return HRTIMER_NORESTART;
  63 }