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=-4.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,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 243C6C2D0A3 for ; Tue, 3 Nov 2020 06:39:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3BFC222B9 for ; Tue, 3 Nov 2020 06:39:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727705AbgKCGjh (ORCPT ); Tue, 3 Nov 2020 01:39:37 -0500 Received: from mga17.intel.com ([192.55.52.151]:58006 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725968AbgKCGjh (ORCPT ); Tue, 3 Nov 2020 01:39:37 -0500 IronPort-SDR: S3koBqzRcXec5ttgu4tG+5FJrp76Dd3gPqSuCLX0koK4+cDhAaZWLUBiTtHxDeWwfZkKoZQr2a 2s8cwQ54G5pg== X-IronPort-AV: E=McAfee;i="6000,8403,9793"; a="148862341" X-IronPort-AV: E=Sophos;i="5.77,447,1596524400"; d="scan'208";a="148862341" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Nov 2020 22:39:36 -0800 IronPort-SDR: 6lkR3ZW/8tjkAqo80ALm8oSLHurpDG7odCSNga5o9RSrrcu8HwE9ZJRrFXmqIOCKNEFsfd2q8r ppdFrrxigaMQ== X-IronPort-AV: E=Sophos;i="5.77,447,1596524400"; d="scan'208";a="470673893" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.239.13.118]) ([10.239.13.118]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Nov 2020 22:39:32 -0800 Subject: Re: [PATCH] KVM: VMX: Enable Notify VM exit To: Paolo Bonzini , Andy Lutomirski , Sean Christopherson Cc: Tao Xu , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , X86 ML , kvm list , LKML References: <20201102061445.191638-1-tao3.xu@intel.com> <20201102173130.GC21563@linux.intel.com> <8e41101c-6278-3773-8754-ffe0763eaeea@redhat.com> From: Xiaoyao Li Message-ID: <06dbea28-4b4a-4f73-2ad2-9b76a8ca4704@intel.com> Date: Tue, 3 Nov 2020 14:39:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <8e41101c-6278-3773-8754-ffe0763eaeea@redhat.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 11/3/2020 2:25 AM, Paolo Bonzini wrote: > On 02/11/20 19:01, Andy Lutomirski wrote: >> What's the point? Surely the kernel should reliably mitigate the >> flaw, and the kernel should decide how to do so. > > There is some slowdown in trapping #DB and #AC unconditionally. Though > for these two cases nobody should care so I agree with keeping the code > simple and keeping the workaround. OK. > Also, why would this trigger after more than a few hundred cycles, > something like the length of the longest microcode loop? HZ*10 seems > like a very generous estimate already. > As Sean said in another mail, 1/10 tick should be a placeholder. Glad to see all of you think it should be smaller. We'll come up with more reasonable candidate once we can test on real silicon.