linux-kernel - [PATCH] KVM: VMX: Check if bus lock vmexit was preempted

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Date:   Sat, 18 Sep 2021 19:30:00 +0800
From:   Hao Xiang <hao.xiang@...ux.alibaba.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, chenyi.qiang@...el.com,
        pbonzini@...hat.com, sean.j.christopherson@...el.com,
        shannon.zhao@...ux.alibaba.com,
        Hao Xiang <hao.xiang@...ux.alibaba.com>
Subject: [PATCH] KVM: VMX: Check if bus lock vmexit was preempted

exit_reason.bus_lock_detected is not only set when bus lock VM exit 
was preempted, in fact, this bit is always set if bus locks are 
detected no matter what the exit_reason.basic is.

So the bus_lock_vmexit handling in vmx_handle_exit should be duplicated 
when exit_reason.basic is EXIT_REASON_BUS_LOCK(74). We can avoid it by 
checking if bus lock vmexit was preempted in vmx_handle_exit.

Signed-off-by: Hao Xiang <hao.xiang@...ux.alibaba.com>
---
 arch/x86/kvm/vmx/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0c2c0d5..5ddf1df 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6054,7 +6054,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	 * still need to exit to user space when bus lock detected to inform
 	 * that there is a bus lock in guest.
 	 */
-	if (to_vmx(vcpu)->exit_reason.bus_lock_detected) {
+	if (to_vmx(vcpu)->exit_reason.bus_lock_detected &&
+			to_vmx(vcpu)->exit_reason.basic != EXIT_REASON_BUS_LOCK) {
 		if (ret > 0)
 			vcpu->run->exit_reason = KVM_EXIT_X86_BUS_LOCK;
 
-- 
1.8.3.1