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KVM: PIT: provide an option to disable interrupt reinjection

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Certain clocks (such as TSC) in older 2.6 guests overaccount for lost
ticks, causing severe time drift. Interrupt reinjection magnifies the
problem.

Provide an option to disable it.

[avi: allow room for expansion in case we want to disable reinjection
      of other timers]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Marcelo Tosatti
2008-12-30 15:55:06 -02:00
committed by Avi Kivity
parent 61a6bd672b
commit 52d939a0bf
5 changed files with 35 additions and 0 deletions
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21
arch/x86/kvm/x86.c
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@@ -993,6 +993,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_NOP_IO_DELAY:
case KVM_CAP_MP_STATE:
case KVM_CAP_SYNC_MMU:
case KVM_CAP_REINJECT_CONTROL:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -1728,6 +1729,15 @@ static int kvm_vm_ioctl_set_pit(struct kvm *kvm, struct kvm_pit_state *ps)
return r;
}
static int kvm_vm_ioctl_reinject(struct kvm *kvm,
struct kvm_reinject_control *control)
{
if (!kvm->arch.vpit)
return -ENXIO;
kvm->arch.vpit->pit_state.pit_timer.reinject = control->pit_reinject;
return 0;
}
/*
* Get (and clear) the dirty memory log for a memory slot.
*/
@@ -1925,6 +1935,17 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = 0;
break;
}
case KVM_REINJECT_CONTROL: {
struct kvm_reinject_control control;
r = -EFAULT;
if (copy_from_user(&control, argp, sizeof(control)))
goto out;
r = kvm_vm_ioctl_reinject(kvm, &control);
if (r)
goto out;
r = 0;
break;
}
default:
;
}