Re: [PATCH] KVM: x86: Add instruction length to VCPU event state

[Gleb Natapov <gleb@redhat.com>]

On Sat, Feb 13, 2010 at 06:49:44PM +0100, Jan Kiszka wrote:
> Gleb Natapov wrote:
> > On Sat, Feb 13, 2010 at 10:51:40AM +0100, Jan Kiszka wrote:
> >> From: Jan Kiszka <jan.kiszka@siemens.com>
> >>
> >> VMX requires a properly set instruction length VM entry field when
> >> trying to inject soft exception and interrupts. We have to preserve this
> >> state across VM save/restore to avoid breaking the re-injection of such
> >> events on Intel. So add it to the new VCPU event state.
> >>
> > We shouldn't re-inject soft exceptions/interrupts after migration, but
> > re-execute instruction instead. Instruction length field doesn't exist
> > on SVM and migration shouldn't expose implementation details.
> > 
> 
> Hmm, then I guess this totally untested patch should fly:
> 
I don't understand what problem are you trying to solve by your patch.
During normal operation event_exit_inst_len will be set to correct
value. After migration rip will point to int instruction an no even will
be pending at all. Here is the patch:

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a1b71da..519f867 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2121,14 +2121,18 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
 {
 	vcpu_load(vcpu);
 
-	events->exception.injected = vcpu->arch.exception.pending;
-	events->exception.nr = vcpu->arch.exception.nr;
-	events->exception.has_error_code = vcpu->arch.exception.has_error_code;
-	events->exception.error_code = vcpu->arch.exception.error_code;
-
-	events->interrupt.injected = vcpu->arch.interrupt.pending;
-	events->interrupt.nr = vcpu->arch.interrupt.nr;
-	events->interrupt.soft = vcpu->arch.interrupt.soft;
+	if (!kvm_exception_is_soft(nr)) {
+		events->exception.injected = vcpu->arch.exception.pending;
+		events->exception.nr = vcpu->arch.exception.nr;
+		events->exception.has_error_code = vcpu->arch.exception.has_error_code;
+		events->exception.error_code = vcpu->arch.exception.error_code;
+	}
+
+	if (!events->interrupt.soft) {
+		events->interrupt.injected = vcpu->arch.interrupt.pending;
+		events->interrupt.nr = vcpu->arch.interrupt.nr;
+		events->interrupt.soft = vcpu->arch.interrupt.soft;
+	}
 
 	events->nmi.injected = vcpu->arch.nmi_injected;
 	events->nmi.pending = vcpu->arch.nmi_pending;
--
			Gleb.