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

Paolo Bonzini
2021-10-26T16:16:06Z

On 25/10/21 22:38, Sasha Levin wrote:
> From: Hao Xiang <hao.xiang@linux.alibaba.com>
>
> [ 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@linux.alibaba.com>
> Message-Id: <1634299161-30101-1-git-send-email-hao.xiang@linux.alibaba.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> 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