Re: [PATCH MANUALSEL 5.14 3/5] KVM: VMX: Remove redundant handling of bus lock vmexit

[Paolo Bonzini]

On 25/10/21 22:38, Sasha Levin wrote:
> From: Hao Xiang <hao.xiang@xxxxxxxxxxxxxxxxx>
>
> [ Upstream commit d61863c66f9b443192997613cd6aeca3f65cc313 ]
>
> Hardware may or may not set exit_reason.bus_lock_detected on BUS_LOCK
> VM-Exits. Dealing with KVM_RUN_X86_BUS_LOCK in handle_bus_lock_vmexit
> could be redundant when exit_reason.basic is EXIT_REASON_BUS_LOCK.
>
> We can remove redundant handling of bus lock vmexit. Unconditionally Set
> exit_reason.bus_lock_detected in handle_bus_lock_vmexit(), and deal with
> KVM_RUN_X86_BUS_LOCK only in vmx_handle_exit().
>
> Signed-off-by: Hao Xiang <hao.xiang@xxxxxxxxxxxxxxxxx>
> Message-Id: <1634299161-30101-1-git-send-email-hao.xiang@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>   arch/x86/kvm/vmx/vmx.c | 15 +++++++++------
>   1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 55de1eb135f9..87150b3c9c5f 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5551,9 +5551,13 @@ static int handle_encls(struct kvm_vcpu *vcpu)
>   
>   static int handle_bus_lock_vmexit(struct kvm_vcpu *vcpu)
>   {
> -	vcpu->run->exit_reason = KVM_EXIT_X86_BUS_LOCK;
> -	vcpu->run->flags |= KVM_RUN_X86_BUS_LOCK;
> -	return 0;
> +	/*
> +	 * Hardware may or may not set the BUS_LOCK_DETECTED flag on BUS_LOCK
> +	 * VM-Exits. Unconditionally set the flag here and leave the handling to
> +	 * vmx_handle_exit().
> +	 */
> +	to_vmx(vcpu)->exit_reason.bus_lock_detected = true;
> +	return 1;
>   }
>   
>   /*
> @@ -6039,9 +6043,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>   	int ret = __vmx_handle_exit(vcpu, exit_fastpath);
>   
>   	/*
> -	 * Even when current exit reason is handled by KVM internally, we
> -	 * still need to exit to user space when bus lock detected to inform
> -	 * that there is a bus lock in guest.
> +	 * 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 (ret > 0)

NACK

No functional change; this time the bot is not doing a good job. :)

Paolo