Re: [patch 1/2] KVM: x86: handle double and triple faults for every exception

[Gleb Natapov <gleb@redhat.com>]

On Sun, Nov 15, 2009 at 02:41:58PM +0200, Avi Kivity wrote:
> On 11/12/2009 02:26 PM, Gleb Natapov wrote:
> >>
> >>-	if (vcpu->arch.exception.pending) {
> >>-		switch(vcpu->arch.exception.nr) {
> >>-		case DF_VECTOR:
> >>-			/* triple fault ->  shutdown */
> >>-			set_bit(KVM_REQ_TRIPLE_FAULT,&vcpu->requests);
> >>-			return;
> >>-		case PF_VECTOR:
> >>-			vcpu->arch.exception.nr = DF_VECTOR;
> >>-			vcpu->arch.exception.error_code = 0;
> >>-			return;
> >>-		default:
> >>-			/* replace previous exception with a new one in a hope
> >>-			   that instruction re-execution will regenerate lost
> >>-			   exception */
> >>-			vcpu->arch.exception.pending = false;
> >>-			break;
> >When exceptions are handled serially previous exception have to be
> >replaced by new one. Think about #PF during #DE. #PF should be handled first
> >before #DE can proceed.
> 
> "replacing" exceptions is dangerous in the case of debug exceptions
> and machine checks, since restarting execution won't recover them.
> 
But not replacing them is not better. No point in re-injecting
exception that causes another exception.

--
			Gleb.