Re: [PATCH 8/9] allow read access to MSR_VM_VR

[Joerg Roedel <joro@8bytes.org>]

On Thu, Oct 30, 2008 at 02:15:23PM -0500, Anthony Liguori wrote:
> Alexander Graf wrote:
> >From: Joerg Roedel <joerg.roedel@amd.com>
> >
> >KVM tries to read the VM_CR MSR to find out if SVM was disabled by
> >the BIOS. So implement read support for this MSR to make nested
> >SVM running.
> >
> >Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
> >Signed-off-by: Alexander Graf <agraf@suse.de>
> >---
> > arch/x86/kvm/svm.c |    3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> >
> >diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> >index 720b610..4582699 100644
> >--- a/arch/x86/kvm/svm.c
> >+++ b/arch/x86/kvm/svm.c
> >@@ -1869,6 +1869,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, 
> >unsigned ecx, u64 *data)
> > 	case MSR_VM_HSAVE_PA:
> > 		*data = 0;
> > 		break;
> >+	case MSR_VM_CR:
> >+		*data = 0;
> >+		break;
> >  
> 
> It would be useful to support setting this value too.  Then we could 
> disable SVM support by writing the MSR in the BIOS.

Things are a bit more complicated here. On real hardware you can't
disable SVM by writing so VM_CR. You have to implement the SVM_KEY
MSR for that. But that should not be too difficult.

Joerg