FAILED: patch "[PATCH] KVM: SEV: Don't terminate SNP VMs on #VMGEXIT without a" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 1797e00bf802d64b859ea18505087daad92019c8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026071620-sporting-snowdrop-2d52@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1797e00bf802d64b859ea18505087daad92019c8 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Fri, 29 May 2026 20:35:43 +0200
Subject: [PATCH] KVM: SEV: Don't terminate SNP VMs on #VMGEXIT without a
 registered GHCB

If the guest attempts a non-MSR #VMGEXIT without the registered GHCB,
return a GHCB_HV_RESP_MALFORMED_INPUT+GHCB_ERR_NOT_REGISTERED error to the
guest instead of exiting KVM_RUN with -EINVAL (and in likelihood killing
the VM).  KVM has already mapped the requested GHCB, i.e. can cleanly
report an error, and so exiting with -EINVAL is completely unjustified.

Fixes: 0c76b1d08280 ("KVM: SEV: Add support to handle GHCB GPA register VMGEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20260529183549.1104619-19-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 6c6a6d663e29..7c2ebc81306f 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4520,9 +4520,12 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 	sev_es_sync_from_ghcb(svm);
 
 	/* SEV-SNP guest requires that the GHCB GPA must be registered */
-	if (is_sev_snp_guest(vcpu) && !ghcb_gpa_is_registered(svm, ghcb_gpa)) {
-		vcpu_unimpl(&svm->vcpu, "vmgexit: GHCB GPA [%#llx] is not registered.\n", ghcb_gpa);
-		return -EINVAL;
+	if (is_sev_snp_guest(vcpu) &&
+	    !ghcb_gpa_is_registered(svm, control->ghcb_gpa)) {
+		vcpu_unimpl(vcpu, "vmgexit: GHCB GPA [%#llx] is not registered.\n",
+			    control->ghcb_gpa);
+		svm_vmgexit_bad_input(svm, GHCB_ERR_NOT_REGISTERED);
+		return 1;
 	}
 
 	ret = sev_es_validate_vmgexit(svm);