From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3B95C433FE for ; Fri, 15 Oct 2021 07:28:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9C2961108 for ; Fri, 15 Oct 2021 07:28:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234603AbhJOHaW (ORCPT ); Fri, 15 Oct 2021 03:30:22 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:33196 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229656AbhJOHaU (ORCPT ); Fri, 15 Oct 2021 03:30:20 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=hao.xiang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0Us6Ki-m_1634282892; Received: from 30.43.96.45(mailfrom:hao.xiang@linux.alibaba.com fp:SMTPD_---0Us6Ki-m_1634282892) by smtp.aliyun-inc.com(127.0.0.1); Fri, 15 Oct 2021 15:28:13 +0800 Message-ID: <8cda9b23-9985-5b59-5d9b-eee4f798fb38@linux.alibaba.com> Date: Fri, 15 Oct 2021 15:28:13 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v2] KVM: VMX: Remove redundant handling of bus lock vmexit Content-Language: en-US To: Xiaoyao Li , kvm@vger.kernel.org Cc: shannon.zhao@linux.alibaba.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, seanjc@google.com References: <1634270265-99421-1-git-send-email-hao.xiang@linux.alibaba.com> <5eb45c93-38aa-cea8-a5c8-cf786c193342@intel.com> From: Hao Xiang In-Reply-To: <5eb45c93-38aa-cea8-a5c8-cf786c193342@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/10/15 14:46, Xiaoyao Li wrote: > On 10/15/2021 11:57 AM, Hao Xiang wrote: >> 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. Force Setting >> exit_reason.bus_lock_detected in handle_bus_lock_vmexit(), and deal with >> KVM_RUN_X86_BUS_LOCK only in vmx_handle_exit(). >> >> Suggested-by: Sean Christopherson >> Signed-off-by: Hao Xiang >> --- >> v1 -> v2: a little modifications of comments >> >>   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 116b089..22be02e 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -5562,9 +5562,13 @@ 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, force setting the flag > >>          so that the logic in vmx_handle_exit() >> +     * doesn't have to handle the flag and the basic exit reason. > > The code itself looks good. > > But the comment is partly incorrect. Now we rely only on the > bus_lock_detected flag so vmx_handle_exit() must check the flag. >Thank you for you advice. Is the following comment ok? /* * Hardware may or may not set the BUS_LOCK_DETECTED flag on BUS_LOCK * VM-Exits. Forcely set the flag here, then check the flag in * vmx_handle_exit() and handle the bus lock vmexit if the flag is * set. */ >> +     */ >> +    to_vmx(vcpu)->exit_reason.bus_lock_detected = true; >> +    return 1; >>   } >>   /* >> @@ -6051,9 +6055,8 @@ 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) >>