2020-11-16 18:15:06

by Paolo Bonzini

Subject: [PATCH] KVM: SVM: check CR4 changes against vcpu->arch

Similarly to what vmx/vmx.c does, use vcpu->arch.cr4 to check if CR4
bits PGE, PKE and OSXSAVE have changed. When switching between VMCB01
and VMCB02, CPUID has to be adjusted every time if CR4.PKE or CR4.OSXSAVE
change; without this patch, instead, CR4 would be checked against the
previous value for L2 on vmentry, and against the previous value for
L1 on vmexit, and CPUID would not be updated.

Signed-off-by: Paolo Bonzini <[email protected]>
---
arch/x86/kvm/svm/svm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 3b53a7ead04b..6dc337b9c231 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1691,7 +1691,7 @@ static bool svm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long host_cr4_mce = cr4_read_shadow() & X86_CR4_MCE;
- unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;
+ unsigned long old_cr4 = vcpu->arch.cr4;

if (npt_enabled && ((old_cr4 ^ cr4) & X86_CR4_PGE))
svm_flush_tlb(vcpu);
--
2.26.2

2020-11-16 22:59:12

by Jim Mattson

Subject: Re: [PATCH] KVM: SVM: check CR4 changes against vcpu->arch

On Mon, Nov 16, 2020 at 10:11 AM Paolo Bonzini <[email protected]> wrote:
>
> Similarly to what vmx/vmx.c does, use vcpu->arch.cr4 to check if CR4
> bits PGE, PKE and OSXSAVE have changed. When switching between VMCB01
> and VMCB02, CPUID has to be adjusted every time if CR4.PKE or CR4.OSXSAVE
> change; without this patch, instead, CR4 would be checked against the
> previous value for L2 on vmentry, and against the previous value for
> L1 on vmexit, and CPUID would not be updated.
>
> Signed-off-by: Paolo Bonzini <[email protected]>
Reviewed-by: Jim Mattson <[email protected]>