FAILED: patch "[PATCH] KVM: TDX: Enable Bus Lock VM exit" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] KVM: TDX: Enable Bus Lock VM exit" failed to apply to 6.18-stable tree

[Sasha Levin]

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 63d196e2e20429de5ba501f1b6059d9b93140007
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107050708-failed-6.18-63d196e2e204@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Thanks,
Sasha

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

From 63d196e2e20429de5ba501f1b6059d9b93140007 Mon Sep 17 00:00:00 2001
From: Xiaoyao Li <xiaoyao.li@intel.com>
Date: Wed, 19 Aug 2026 17:49:02 +0800
Subject: [PATCH] KVM: TDX: Enable Bus Lock VM exit

Enable Bus Lock VM exit functionality for TDX guests.

Bus Lock VM exit is an existing feature supported by KVM.  Userspace can
enable Bus Lock VM exit through KVM_BUS_LOCK_DETECTION_EXIT when it's
reported as supported.  However, KVM reports the support of this CAP
just based on the hardware capability but doesn't differentiate between
VMX and TDX.  This leads to the issue that userspace can enable this cap
for TDX guests without getting an error, but the feature is not actually
enabled because KVM doesn't call the TDX module API to program the
relevant TD VMCS fields.

Enable Bus Lock VM exit for TDX guests by programming the
BUS_LOCK_DETECTION control in the TD VMCS and by adding the exit handler.

Note, there is no enumeration bit for this feature by TDX module because
all TDX modules support it and allow to set the TD VMCS as long as the
hardware supports the feature.

Fixes: 161d34609f9b ("KVM: TDX: Make TDX VM type supported")
Cc: stable@vger.kernel.org
Originally-by: Chenyi Qiang <chenyi.qiang@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://patch.msgid.link/20260819094903.3060020-9-xiaoyao.li@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/tdx.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 6762724a80f57..3d093efe8820b 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2050,7 +2050,7 @@ int tdx_complete_emulated_msr(struct kvm_vcpu *vcpu, int err)
 }
 
 
-int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
+static int __tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 {
 	struct vcpu_tdx *tdx = to_tdx(vcpu);
 	u64 vp_enter_ret = tdx->vp_enter_ret;
@@ -2151,6 +2151,8 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 	case EXIT_REASON_NOTIFY:
 		/* NMI blocking state is handled by TDX module */
 		return __vt_handle_notify(vcpu, vmx_get_exit_qual(vcpu));
+	case EXIT_REASON_BUS_LOCK:
+		return vt_handle_bus_lock_vmexit(vcpu);
 	default:
 		break;
 	}
@@ -2160,6 +2162,22 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 	return 0;
 }
 
+int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
+{
+	int ret = __tdx_handle_exit(vcpu, fastpath);
+
+	/* Exit to user space when bus lock was detected */
+	if (vmx_get_exit_reason(vcpu).bus_lock_detected) {
+		if (ret > 0) {
+			vcpu->run->exit_reason = KVM_EXIT_X86_BUS_LOCK;
+			ret = 0;
+		}
+
+		vcpu->run->flags |= KVM_RUN_X86_BUS_LOCK;
+	}
+	return ret;
+}
+
 void tdx_get_exit_info(struct kvm_vcpu *vcpu, u32 *reason,
 		u64 *info1, u64 *info2, u32 *intr_info, u32 *error_code)
 {
@@ -3186,6 +3204,10 @@ static int tdx_vcpu_init(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
 				vcpu->kvm->arch.notify_window);
 	}
 
+	if (vcpu->kvm->arch.bus_lock_detection_enabled)
+		td_vmcs_setbit32(tdx, SECONDARY_VM_EXEC_CONTROL,
+				 SECONDARY_EXEC_BUS_LOCK_DETECTION);
+
 	tdx->state = VCPU_TD_STATE_INITIALIZED;
 
 	return 0;
-- 
2.53.0