[PATCH] svm: Avoid VINTR injection during NMI shadow

[PATCH] svm: Avoid VINTR injection during NMI shadow

[Wei Wang2]

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Hi,
I had observed that if xen injects and intercepts VINTR during NMI shadow, and 
if the xen injects NMI into guest at a very hight frequency, guest vcpu will 
hang. Attached patch avoids VINTR injection when guest is handling a NMI.

Thanks,

Wei
Signed-off-by: Wei Wang <wei.wang2@amd.com>
Reviewed-by: Wei Huang<wei.huang2@amd.com>
--
Legal Information:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34
85609 Dornach b. München

Geschäftsführer: Andrew Bowd, Thomas M. McCoy, Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis München
Registergericht München, HRB Nr. 43632

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diff -r e6f751ed8e38 xen/arch/x86/hvm/svm/intr.c
--- a/xen/arch/x86/hvm/svm/intr.c	Tue Mar 09 10:00:37 2010 +0000
+++ b/xen/arch/x86/hvm/svm/intr.c	Fri May 07 16:15:58 2010 +0200
@@ -92,6 +92,10 @@ static void enable_intr_window(struct vc
      * track 'NMI blocking' from NMI injection until IRET. This can be done
      * quite easily in software by intercepting the unblocking IRET.
      */
+
+    if ( vmcb->general1_intercepts & GENERAL1_INTERCEPT_IRET )
+        return;
+
     intr = vmcb->vintr;
     intr.fields.irq     = 1;
     intr.fields.vector  = 0;

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Re: [PATCH] svm: Avoid VINTR injection during NMI shadow

[Keir Fraser]

I think the if statement should be:
 if ((vmcb->general1_intercepts & GENERAL1_INTERCEPT_IRET) &&
     (intack.source == hvm_intsrc_nmi))
     return;

Which I think deals properly and specifically with this hang problem.

What do you think?

 -- Keir

On 07/05/2010 15:41, "Wei Wang2" <wei.wang2@amd.com> wrote:

> Hi,
> I had observed that if xen injects and intercepts VINTR during NMI shadow, and
> if the xen injects NMI into guest at a very hight frequency, guest vcpu will
> hang. Attached patch avoids VINTR injection when guest is handling a NMI.
> 
> Thanks,
> 
> Wei
> Signed-off-by: Wei Wang <wei.wang2@amd.com>
> Reviewed-by: Wei Huang<wei.huang2@amd.com>
> --
> Legal Information:
> Advanced Micro Devices GmbH
> Karl-Hammerschmidt-Str. 34
> 85609 Dornach b. München
> 
> Geschäftsführer: Andrew Bowd, Thomas M. McCoy, Giuliano Meroni
> Sitz: Dornach, Gemeinde Aschheim, Landkreis München
> Registergericht München, HRB Nr. 43632

Re: [PATCH] svm: Avoid VINTR injection during NMI shadow

[Wei Wang2]

Totally agree,  you are are right only NMI injection should be avoid.
I have tested that the new condition works well. Thanks.
Wei

On Friday 07 May 2010 18:56:32 Keir Fraser wrote:
> I think the if statement should be:
>  if ((vmcb->general1_intercepts & GENERAL1_INTERCEPT_IRET) &&
>      (intack.source == hvm_intsrc_nmi))
>      return;
>
> Which I think deals properly and specifically with this hang problem.
>
> What do you think?
>
>  -- Keir
>
> On 07/05/2010 15:41, "Wei Wang2" <wei.wang2@amd.com> wrote:
> > Hi,
> > I had observed that if xen injects and intercepts VINTR during NMI
> > shadow, and if the xen injects NMI into guest at a very hight frequency,
> > guest vcpu will hang. Attached patch avoids VINTR injection when guest is
> > handling a NMI.
> >
> > Thanks,
> >
> > Wei
> > Signed-off-by: Wei Wang <wei.wang2@amd.com>
> > Reviewed-by: Wei Huang<wei.huang2@amd.com>
> > --
> > Legal Information:
> > Advanced Micro Devices GmbH
> > Karl-Hammerschmidt-Str. 34
> > 85609 Dornach b. München
> >
> > Geschäftsführer: Andrew Bowd, Thomas M. McCoy, Giuliano Meroni
> > Sitz: Dornach, Gemeinde Aschheim, Landkreis München
> > Registergericht München, HRB Nr. 43632