2021-05-07 17:39:24

by Sean Christopherson

Subject: [PATCH 1/2] KVM: SVM: Update EFER software model on CR0 trap for SEV-ES

For protected guests, a.k.a. SEV-ES guests, update KVM's model of EFER
when processing the side effect of the CPU entering long mode when paging
is enabled. The whole point of intercepting CR0/CR4/EFER is to keep
KVM's software model up-to-date.

Fixes: f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES")
Reported-by: Peter Gonda <[email protected]>
Cc: [email protected]
Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/svm/svm.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index a7271f31df47..d271fe8e58de 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1696,15 +1696,17 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
u64 hcr0 = cr0;

#ifdef CONFIG_X86_64
- if (vcpu->arch.efer & EFER_LME && !vcpu->arch.guest_state_protected) {
+ if (vcpu->arch.efer & EFER_LME) {
if (!is_paging(vcpu) && (cr0 & X86_CR0_PG)) {
vcpu->arch.efer |= EFER_LMA;
- svm->vmcb->save.efer |= EFER_LMA | EFER_LME;
+ if (!vcpu->arch.guest_state_protected)
+ svm->vmcb->save.efer |= EFER_LMA | EFER_LME;
}

if (is_paging(vcpu) && !(cr0 & X86_CR0_PG)) {
vcpu->arch.efer &= ~EFER_LMA;
- svm->vmcb->save.efer &= ~(EFER_LMA | EFER_LME);
+ if (!vcpu->arch.guest_state_protected)
+ svm->vmcb->save.efer &= ~(EFER_LMA | EFER_LME);
}
}
#endif
--
2.31.1.607.g51e8a6a459-goog

2021-05-07 23:16:40

by Tom Lendacky

Subject: Re: [PATCH 1/2] KVM: SVM: Update EFER software model on CR0 trap for SEV-ES

On 5/7/21 11:59 AM, Sean Christopherson wrote:
> For protected guests, a.k.a. SEV-ES guests, update KVM's model of EFER
> when processing the side effect of the CPU entering long mode when paging
> is enabled. The whole point of intercepting CR0/CR4/EFER is to keep
> KVM's software model up-to-date.
>
> Fixes: f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES")
> Reported-by: Peter Gonda <[email protected]>
> Cc: [email protected]
> Signed-off-by: Sean Christopherson <[email protected]>

Acked-by: Tom Lendacky <[email protected]>

> ---
> arch/x86/kvm/svm/svm.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index a7271f31df47..d271fe8e58de 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1696,15 +1696,17 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
> u64 hcr0 = cr0;
>
> #ifdef CONFIG_X86_64
> - if (vcpu->arch.efer & EFER_LME && !vcpu->arch.guest_state_protected) {
> + if (vcpu->arch.efer & EFER_LME) {
> if (!is_paging(vcpu) && (cr0 & X86_CR0_PG)) {
> vcpu->arch.efer |= EFER_LMA;
> - svm->vmcb->save.efer |= EFER_LMA | EFER_LME;
> + if (!vcpu->arch.guest_state_protected)
> + svm->vmcb->save.efer |= EFER_LMA | EFER_LME;
> }
>
> if (is_paging(vcpu) && !(cr0 & X86_CR0_PG)) {
> vcpu->arch.efer &= ~EFER_LMA;
> - svm->vmcb->save.efer &= ~(EFER_LMA | EFER_LME);
> + if (!vcpu->arch.guest_state_protected)
> + svm->vmcb->save.efer &= ~(EFER_LMA | EFER_LME);
> }
> }
> #endif
>