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 CC523C433EF for ; Fri, 15 Oct 2021 08:43:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A953360FC3 for ; Fri, 15 Oct 2021 08:43:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235827AbhJOIpv (ORCPT ); Fri, 15 Oct 2021 04:45:51 -0400 Received: from mga18.intel.com ([134.134.136.126]:15959 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229667AbhJOIpu (ORCPT ); Fri, 15 Oct 2021 04:45:50 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10137"; a="214813451" X-IronPort-AV: E=Sophos;i="5.85,375,1624345200"; d="scan'208";a="214813451" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Oct 2021 01:43:44 -0700 X-IronPort-AV: E=Sophos;i="5.85,375,1624345200"; d="scan'208";a="442457306" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.239.13.123]) ([10.239.13.123]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Oct 2021 01:43:42 -0700 Message-ID: <11416416-8fc8-f4db-71d6-5205f3b7515e@intel.com> Date: Fri, 15 Oct 2021 16:43:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.2.0 Subject: Re: [PATCH v2] KVM: VMX: Remove redundant handling of bus lock vmexit Content-Language: en-US To: Hao Xiang , 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> <8cda9b23-9985-5b59-5d9b-eee4f798fb38@linux.alibaba.com> From: Xiaoyao Li In-Reply-To: <8cda9b23-9985-5b59-5d9b-eee4f798fb38@linux.alibaba.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 10/15/2021 3:28 PM, Hao Xiang wrote: > > > 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. >  */ (I'm not sure if forcely is a valid word) how about /* * Hardware may or may not set the BUS_LOCK_DETECTED flag on BUS_LOCK * VM Exit. Unconditionally set the flag here and leave the handling to * vmx_handle_exit(). */ >>> +     */ >>> +    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) >>>