On Wed, Sep 06, 2023, Tom Lendacky wrote:
> On 9/6/23 15:11, Sean Christopherson wrote:
> > On Wed, Sep 06, 2023, Tom Lendacky wrote:
> > > On 9/6/23 10:14, Peter Gonda wrote:
> > > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > > > index 956726d867aa..cecf6a528c9b 100644
> > > > --- a/arch/x86/kvm/svm/svm.c
> > > > +++ b/arch/x86/kvm/svm/svm.c
> > > > @@ -2131,12 +2131,14 @@ static int shutdown_interception(struct kvm_vcpu *vcpu)
> > > > * The VM save area has already been encrypted so it
> > > > * cannot be reinitialized - just terminate.
> > > > */
> > > > - if (sev_es_guest(vcpu->kvm))
> > > > - return -EINVAL;
> > > > + if (sev_es_guest(vcpu->kvm)) {
> > > > + kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;
> > > > + return 0;
> > > > + }
> > >
> > > Just a nit... feel free to ignore, but, since KVM_EXIT_SHUTDOWN is also set
> > > at the end of the function and I don't think kvm_vcpu_reset() clears the
> > > value from kvm_run, you could just set kvm_run->exit_reason on entry and
> > > just return 0 early for an SEV-ES guest.
> >
> > kvm_run is writable by userspace though, so KVM can't rely on kvm_run->exit_reason
> > for correctness.
> >
> > And IIUC, the VMSA is also toast, i.e. doing anything other than marking the VM
> > dead is futile, no?
>
> I was just saying that "kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;" is in the
> shutdown_interception() function twice now (at both exit points of the
> function) and can probably just be moved to the top of the function and be
> common for both exit points, now, right?
>
> I'm not saying to get rid of it, just set it sooner.
Ah, I thought you were saying bail early from kvm_vcpu_reset(). I agree that not
having completely split logic would be ideal. What about this?
/*
* VMCB is undefined after a SHUTDOWN intercept. INIT the vCPU to put
* the VMCB in a known good state. Unfortuately, KVM doesn't have
* KVM_MP_STATE_SHUTDOWN and can't add it without potentially breaking
* userspace. At a platform view, INIT is acceptable behavior as
* there exist bare metal platforms that automatically INIT the CPU
* in response to shutdown.
*
* The VM save area for SEV-ES guests has already been encrypted so it
* cannot be reinitialized, i.e. synthesizing INIT is futile.
*/
if (!sev_es_guest(vcpu->kvm)) {
clear_page(svm->vmcb);
kvm_vcpu_reset(vcpu, true);
}
kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;
return 0;
