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 X-Spam-Level: X-Spam-Status: No, score=-8.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67C9FC4320A for ; Tue, 10 Aug 2021 12:50:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C3D060EFF for ; Tue, 10 Aug 2021 12:50:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240831AbhHJMuX (ORCPT ); Tue, 10 Aug 2021 08:50:23 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24415 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240821AbhHJMuW (ORCPT ); Tue, 10 Aug 2021 08:50:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628599800; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CrJJsbAkLGNgRBl30mWJDu4C6R0HhYbl466l69qWuNo=; b=fx/xkC8VzAb1I4cFNXVRR77w4zZ6D+Tyq0yMfCPiv6t15C+qh7L/S3/bx07tMahujVr/Ej e/TqYaOD4XMTjibxWGksm9tKhK9RJ8TdGR5KaOP7tmX0KfenMgX4wlXDJIHpqOZ2ehYCgj QWkcNDJzSIC+sAicVaLTrJlxrIslKfU= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-294-SfUCvnaPOyiV9Qt4y7GZyw-1; Tue, 10 Aug 2021 08:49:59 -0400 X-MC-Unique: SfUCvnaPOyiV9Qt4y7GZyw-1 Received: by mail-ed1-f70.google.com with SMTP id v20-20020aa7d9d40000b02903be68450bf3so2913769eds.23 for ; Tue, 10 Aug 2021 05:49:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=CrJJsbAkLGNgRBl30mWJDu4C6R0HhYbl466l69qWuNo=; b=otbDRNysRE0GxeB5cy/ASDSh0mLacx6tL23rciHIKe2a8tOS25oXv7p8B1fNB0+EXb bXz+Dlfrx6ADV4oLc9JcIl5yzU27hY1z96MZB3aRbqKzW4jDrOgxpqvLOGcH6S8TwFR+ p2fvBxEf5uG1ympb9AD+jDrLx2VkpYlF8TCf4CcYV/Dt7R59r+Oh3HbO4zTUM8ZnlZ9h nInbf3s47mXz5Q/gd0OT/CcBmk1YehtQGiggcP7Ry+/d4kw5c3JIuOI/wHZgVpDWJVcS DbQKcLJeuV67qX6AlBxf8BzWn3HOSf31/lFqYiAU6RCE2TfOjt8+Io26tAHCrCn+4Va9 bmsg== X-Gm-Message-State: AOAM532VeucIbYRTWJTvGJV4p01r5+43O7c6QOgsczNdkrKLmIdXxki+ 8CtvChcU8tea1aw7qp0+l1FaRycC+WKHg/alkzncnj/6OqjYcd5jL/GbsQb/AfXP4bBubIqBuPe C4Vu4zeqiAZBS3A9uybuzmQZM X-Received: by 2002:a17:906:3fd7:: with SMTP id k23mr10765204ejj.176.1628599797945; Tue, 10 Aug 2021 05:49:57 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxFLHW5kax97qIP8ewfDh6uPQkc89girs1g1d7+ETW92PSAenZdEwjl94gWbyXPERUKhx8NjQ== X-Received: by 2002:a17:906:3fd7:: with SMTP id k23mr10765194ejj.176.1628599797728; Tue, 10 Aug 2021 05:49:57 -0700 (PDT) Received: from [192.168.10.118] ([93.56.169.140]) by smtp.gmail.com with ESMTPSA id cb4sm6818998ejb.72.2021.08.10.05.49.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Aug 2021 05:49:57 -0700 (PDT) Subject: Re: [PATCH V2 2/3] KVM: X86: Set the hardware DR6 only when KVM_DEBUGREG_WONT_EXIT To: Lai Jiangshan , Lai Jiangshan , linux-kernel@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org References: <20210809174307.145263-1-jiangshanlai@gmail.com> <20210809174307.145263-2-jiangshanlai@gmail.com> <68ed0f5c-40f1-c240-4ad1-b435568cf753@redhat.com> <45fef019-8bd9-2acb-bd53-1243a8a07c4e@linux.alibaba.com> <7f86316b-5010-5250-4223-5a4d62f942c8@linux.alibaba.com> From: Paolo Bonzini Message-ID: Date: Tue, 10 Aug 2021 14:49:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <7f86316b-5010-5250-4223-5a4d62f942c8@linux.alibaba.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/08/21 12:46, Lai Jiangshan wrote: > I'm OK with it. But I don't think the sketched idea would cause DR6 to > be marked uselessly as dirty in SVM. It doesn't mark it dirty if the > value is unchanged, and the value is always DR6_ACTIVE_LOW except when > it just clears KVM_DEBUGREG_WONT_EXIT. It would be marked dirty if it is not DR6_ACTIVE_LOW, because it would be set first to DR6_ACTIVE_LOW in svm_handle_exit and then set back to the guest value on the next entry. Paolo