KVM: SVM: Update SEV-ES shutdown intercepts with more metadata

Currently if an SEV-ES VM shuts down userspace sees KVM_RUN struct with
only errno=EINVAL. This is a very limited amount of information to debug
the situation. Instead return KVM_EXIT_SHUTDOWN to alert userspace the VM
is shutting down and is not usable any further.

Signed-off-by: Peter Gonda <pgonda@google.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230907162449.1739785-1-pgonda@google.com
[sean: tweak changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9507df93f410a631b1b06acd9937bea881e7b5c9..f36a6d819280ad304cd35d2c06aaa2978e9f4a8f 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2203,12 +2203,6 @@ static int shutdown_interception(struct kvm_vcpu *vcpu)
        struct kvm_run *kvm_run = vcpu->run;
        struct vcpu_svm *svm = to_svm(vcpu);
 
-       /*
-        * The VM save area has already been encrypted so it
-        * cannot be reinitialized - just terminate.
-        */
-       if (sev_es_guest(vcpu->kvm))
-               return -EINVAL;
 
        /*
         * VMCB is undefined after a SHUTDOWN intercept.  INIT the vCPU to put
@@ -2217,9 +2211,14 @@ static int shutdown_interception(struct kvm_vcpu *vcpu)
         * 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.
         */
-       clear_page(svm->vmcb);
-       kvm_vcpu_reset(vcpu, true);
+       if (!sev_es_guest(vcpu->kvm)) {
+               clear_page(svm->vmcb);
+               kvm_vcpu_reset(vcpu, true);
+       }
 
        kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;
        return 0;