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

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Date:   Tue, 5 Sep 2023 13:58:04 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: SEV: Update SEV-ES shutdown intercepts with more metadata

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.

> Signed-off-by: Peter Gonda <pgonda@...gle.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: x86@...nel.org
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> 
> ---
> 
> 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.