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

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Date:   Tue,  5 Sep 2023 09:10:48 -0700
From:   Peter Gonda <pgonda@...gle.com>
To:     kvm@...r.kernel.org
Cc:     Peter Gonda <pgonda@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.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: [PATCH] KVM: SEV: Update SEV-ES shutdown intercepts with more metadata

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.

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.

---

 arch/x86/kvm/svm/svm.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 956726d867aa..547526616d60 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2131,12 +2131,16 @@ 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)) {
+		vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
+		vcpu->run->system_event.type = KVM_SYSTEM_EVENT_SEV_TERM;
+		kvm_vm_dead(vcpu->kvm);
+		return 0;
+	}
 
 	/*
 	 * 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
-- 
2.42.0.283.g2d96d420d3-goog