Messages in this thread | | | Date | Mon, 14 Sep 2020 14:51:45 -0700 | From | Sean Christopherson <> | Subject | Re: [RFC PATCH 28/35] KVM: X86: Update kvm_skip_emulated_instruction() for an SEV-ES guest |
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On Mon, Sep 14, 2020 at 03:15:42PM -0500, Tom Lendacky wrote: > From: Tom Lendacky <thomas.lendacky@amd.com> > > The register state for an SEV-ES guest is encrypted so the value of the > RIP cannot be updated. For an automatic exit, the RIP will be advanced > as necessary. For a non-automatic exit, it is up to the #VC handler in > the guest to advance the RIP. > > Add support to skip any RIP updates in kvm_skip_emulated_instruction() > for an SEV-ES guest.
Is there a reason this can't be handled in svm? E.g. can KVM be reworked to effectively split the emulation logic so that it's a bug for KVM to end up trying to modify RIP?
Also, patch 06 modifies SVM's skip_emulated_instruction() to skip the RIP update, but keeps the "svm_set_interrupt_shadow(vcpu, 0)" logic. Seems like either that change or this one is wrong.
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> > --- > arch/x86/kvm/x86.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 23564d02d158..1dbdca607511 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6874,13 +6874,17 @@ static int kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu) > > int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu) > { > - unsigned long rflags = kvm_x86_ops.get_rflags(vcpu); > + unsigned long rflags; > int r; > > r = kvm_x86_ops.skip_emulated_instruction(vcpu); > if (unlikely(!r)) > return 0; > > + if (vcpu->arch.vmsa_encrypted) > + return 1; > + > + rflags = kvm_x86_ops.get_rflags(vcpu); > /* > * rflags is the old, "raw" value of the flags. The new value has > * not been saved yet. > -- > 2.28.0 >
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