Re: [PATCH V2] KVM: SEV: Update SEV-ES shutdown intercepts with more metadata

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On 9/6/23 10:14, Peter Gonda wrote:
Currently if an SEV-ES VM shuts down userspace sees KVM_RUN struct with

s/down userspace/down, userspace/

only the INVALID_ARGUMENT. This is a very limited amount of information
to debug the situation. Instead KVM can return a
KVM_EXIT_SHUTDOWN to alert userspace the VM is shutting down and
is not usable any further.

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

---
  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 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.

Overall, though:

Acked-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

Thanks,
Tom

/*
  	 * VMCB is undefined after a SHUTDOWN intercept.  INIT the vCPU to put
-	 * the VMCB in a known good state.  Unfortuately, KVM doesn't have
+	 * the VMCB in a known good state.  Unfortunately, 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



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