On Tue, Mar 11, 2014 at 07:11:18PM +0100, Radim Krčmář wrote:
> We always disable cr8 intercept in its handler, but only re-enable it
> if handling KVM_REQ_EVENT, so there can be a window where we do not
> intercept cr8 writes, which allows an interrupt to disrupt a higher
> priority task.
>
> Fix this by disabling intercepts in the same function that re-enables
> them when needed. This fixes BSOD in Windows 2008.
>
> Cc: <sta...@vger.kernel.org>
> Signed-off-by: Radim Krčmář <rkrc...@redhat.com>
> ---
> arch/x86/kvm/svm.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 64d9bb9..f676c18 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3003,10 +3003,8 @@ static int cr8_write_interception(struct vcpu_svm *svm)
> u8 cr8_prev = kvm_get_cr8(&svm->vcpu);
> /* instruction emulation calls kvm_set_cr8() */
> r = cr_interception(svm);
> - if (irqchip_in_kernel(svm->vcpu.kvm)) {
> - clr_cr_intercept(svm, INTERCEPT_CR8_WRITE);
> + if (irqchip_in_kernel(svm->vcpu.kvm))
> return r;
> - }
> if (cr8_prev <= kvm_get_cr8(&svm->vcpu))
> return r;
> kvm_run->exit_reason = KVM_EXIT_SET_TPR;
> @@ -3568,6 +3566,8 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu,
> int tpr, int irr)
> if (is_guest_mode(vcpu) && (vcpu->arch.hflags & HF_VINTR_MASK))
> return;
>
> + clr_cr_intercept(svm, INTERCEPT_CR8_WRITE);
> +
> if (irr == -1)
> return;
Shouldnt IRR be injected if TPR < IRR ? (via KVM_REQ_EVENT).
1) IRR has interrupt 10.
2) TPR now 9 due to CR8 write.
3) 10 should be injected.
Also not clearing the intercept can cause continuous CR8 writes to
exit until KVM_REQ_EVENT ?
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