[PATCH] disable C1E for HVM guest

[PATCH] disable C1E for HVM guest

[Christoph Egger]

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Hi,

attached patch disables C1E in HVM guests.
This also fixes a guest crash via #GP
on cross-vendor migration.

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>

-- 
---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Jochen Polster, Thomas M. McCoy, Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632

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diff -r c9a35fb19e75 xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c	Thu Mar 12 15:08:08 2009 +0000
+++ b/xen/arch/x86/hvm/hvm.c	Mon Mar 12 16:36:16 2009 +0100
@@ -1776,6 +1776,15 @@ int hvm_msr_read_intercept(struct cpu_us
         msr_content = var_range_base[index];
         break;
 
+    case MSR_K8_ENABLE_C1E:
+         /* There's no point in letting the guest see C-States.
+          * Further, this AMD-only register may be accessed if this HVM guest
+          * has been migrated to an Intel host. This fixes a guest crash
+          * in this case.
+          */
+         msr_content = 0;
+         break;
+
     default:
         return hvm_funcs.msr_read_intercept(regs);
     }

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Re: [PATCH] disable C1E for HVM guest

[Keir Fraser]

On 12/03/2009 15:47, "Christoph Egger" <Christoph.Egger@amd.com> wrote:

> attached patch disables C1E in HVM guests.
> This also fixes a guest crash via #GP
> on cross-vendor migration.
> 
> Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>

Belongs in the SVM-specific MSR read intercept hook in svm.c?

 -- Keir

Re: [PATCH] disable C1E for HVM guest

[Christoph Egger]

On Thursday 12 March 2009 16:57:11 Keir Fraser wrote:
> On 12/03/2009 15:47, "Christoph Egger" <Christoph.Egger@amd.com> wrote:
> > attached patch disables C1E in HVM guests.

> > This also fixes a guest crash via #GP
> > on cross-vendor migration.

> >
> > Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
>
> Belongs in the SVM-specific MSR read intercept hook in svm.c?

No, because this MSR doesn't exist on Intel.

-- 
---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Jochen Polster, Thomas M. McCoy, Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632