FAILED: patch "[PATCH] KVM: TDX: Stuff exit_reason with UNDEFINED on" 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 e5f1d62c59aea4f270773de1bf6e8867f5b1124c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110443-stage-reproach-62d3@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From e5f1d62c59aea4f270773de1bf6e8867f5b1124c Mon Sep 17 00:00:00 2001
From: Xiaoyao Li <xiaoyao.li@intel.com>
Date: Wed, 19 Aug 2026 17:48:59 +0800
Subject: [PATCH] KVM: TDX: Stuff exit_reason with UNDEFINED on
 wait_for_sept_zap return

Forcefully update the exit_reason to KVM's "standard" EXIT_REASON_UNDEFINED
if tdx_vcpu_run() bails without trying to run the vCPU because KVM needs to
wait for an in-progress S-EPT zap to complete.  This avoids handling the
previous exit multiple times due to a stale exit_reason.

Fixes: 4b2abc49712b ("KVM: TDX: Kick off vCPUs when SEAMCALL is busy during TD page removal")
Cc: stable@vger.kernel.org
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://patch.msgid.link/20260819094903.3060020-6-xiaoyao.li@intel.com
[sean: use EXIT_REASON_UNDEFINED, drop comment about bits 31:16]
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index f4d74c02fa1e..6762724a80f5 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1085,8 +1085,16 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 	 * allowing vCPU entry to avoid contention with tdh_vp_enter() and
 	 * TDCALLs.
 	 */
-	if (unlikely(READ_ONCE(to_kvm_tdx(vcpu->kvm)->wait_for_sept_zap)))
+	if (unlikely(READ_ONCE(to_kvm_tdx(vcpu->kvm)->wait_for_sept_zap))) {
+		/*
+		 * The vCPU never entered the guest, but this looks like a
+		 * handled exit to the caller.  Synthesize an invalid exit
+		 * reason so the previous exit's stale value isn't consumed
+		 * a second time.
+		 */
+		vt->exit_reason.full = EXIT_REASON_UNDEFINED;
 		return EXIT_FASTPATH_EXIT_HANDLED;
+	}
 
 	trace_kvm_entry(vcpu, run_flags & KVM_RUN_FORCE_IMMEDIATE_EXIT);