On Tue, Feb 26, 2008 at 03:02:31PM +0200, Avi Kivity wrote:
> Joerg Roedel wrote:
> >In the current inject_page_fault path KVM only checks if there is another PF
> >pending and injects a DF then. But it has to check for a pendig DF too to
> >detect a shutdown condition in the VCPU. If this is not detected the VCPU
> >goes
> >to a PF -> DF -> PF loop when it should triple fault. This patch detects this
> >condition and handles it with an KVM_SHUTDOWN exit to userspace. As a side
> >effect it fixes the following warning when trying to reboot a SMP guest on
> >SVM:
> >diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> >index 1af0ceb..01708b7 100644
> >--- a/arch/x86/kvm/paging_tmpl.h
> >+++ b/arch/x86/kvm/paging_tmpl.h
> >@@ -366,8 +366,9 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t
> >addr,
> > * - normal guest page fault due to the guest pte marked not present, not
> > * writable, or not executable
> > *
> >- * Returns: 1 if we need to emulate the instruction, 0 otherwise, or
> >- * a negative value on error.
> >+ * Returns: 2 if the vcpu triple faulted
> >+ * 1 if we need to emulate the instruction
> >+ * 0 otherwise, or a negative value on error.
> > */
> >
>
> This is a little icky. What about setting vcpu->requests bit
> KVM_REQ_TRIPLE_FAULT and checking it on the next entry?
>
> The check is zero cost since we check vcpu->requests anyway. We can use this
> for other situations as well (like setting cr3 to mmio space, bad paravirt
> mmio operation, etc.)
Ah, right. This will be much simpler and cleaner. I will send an updated
patch.
Joerg
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