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SubjectRe: [PATCH] release kvmclock page on reset
On 2011-01-28 20:48, Glauber Costa wrote:
> Up to know, we were relying on guest cooperation to turn off kvmclock.
> I just realized that even though this is fine and nice, a more robust
> method is to (also) turn it off on vcpu_reset on the hypervisor side.
> This will protect us against reboots, and we don't expect the guest
> to reset its cpu during normal operation anyway.
>
> Signed-off-by: Glauber Costa <glommer@redhat.com>
> ---
> arch/x86/kvm/x86.c | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bcc0efc..38b55b3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5878,6 +5878,11 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
> kvm_make_request(KVM_REQ_EVENT, vcpu);
> vcpu->arch.apf.msr_val = 0;
>
> + if (vcpu->arch.time_page) {
> + kvm_release_page_dirty(vcpu->arch.time_page);
> + vcpu->arch.time_page = NULL;
> + }
> +

kvm_arch_vcpu_reset is only called on vcpu setup and when it receives a
sipi (provided in-kernel irqchip is in use). If you want this page to be
consistently reset on guest reboot, you have to trigger this from user
space. But I thought we are doing this already in qemu, don't we?

Jan

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