Re: [PATCH] KVM: SEV: Update SEV-ES shutdown intercepts with more metadata

[Peter Gonda]

On Tue, Sep 5, 2023 at 2:58 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Tue, Sep 05, 2023, Peter Gonda wrote:
> > Currently if an SEV-ES VM shuts down userspace sees KVM_RUN struct with
> > only the INVALID_ARGUMENT. This is a very limited amount of information
> > to debug the situation. Instead KVM can return a
> > KVM_SYSTEM_EVENT_SEV_TERM to alert userspace the VM is shutting down and
> > is not usable any further. This latter point can be enforced using the
> > kvm_vm_dead() functionality.
>
> Add the kvm_vm_dead() thing in a separate patch.  If we want to actually harden
> KVM against consuming a garbage VMSA then we do need to mark the VM dead, but on
> the other hand that will block _all_ KVM ioctls(), which will make debug even
> harder.

Will do. Do we have better functionality for just blocking running the vCPU?

>
> > Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > Cc: Joerg Roedel <joro@xxxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: kvm@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> >
> > ---
> >
> > I am not sure if this is the right path forward maybe just returning
> > KVM_EXIT_SHUTDOWN is better. But the current behavior is very unhelpful.
>
> Ya, KVM_EXIT_SHUTDOWN is better, we should leave KVM_SYSTEM_EVENT_SEV_TERM to
> explicit "requests" from the guest.

Sounds good to me. I'll send a V2 that just updates to KVM_EXIT_SHUTDOWN.