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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 C5BEEC04AAC for ; Mon, 20 May 2019 10:35:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A785220862 for ; Mon, 20 May 2019 10:35:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731625AbfETKfB (ORCPT ); Mon, 20 May 2019 06:35:01 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:40524 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731376AbfETKfA (ORCPT ); Mon, 20 May 2019 06:35:00 -0400 Received: by mail-wm1-f65.google.com with SMTP id 15so8423954wmg.5 for ; Mon, 20 May 2019 03:34:59 -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=TDeq1R0ZlxS3eYDtruCGOeX8Ha3Jxa2VQZkw5KkPaxY=; b=BRZpdPbCwDQ2OqC+pdmDexHkdOLyTpjhaJ9i/JvF3rLkiusfyWNZgNVksRxyYAxLqa k+D6LMqxXei4AYUNP4yNqpvihY8KQPOFo18oQwcfADnVxFBOUUyAeTesCw+EDfAIUmGT 9XmmLMssjerUAcEJ5IhzDtcc4sqqGhqCBpA8QkZ7XtZX0nGtDtwtjhE4brjBoTFqCi9V L7QALMORJv12avOlEKHW5/ZnNE8R00ehSrsPTa7d+F2XVRxLorZuxHGTwn38KhvDiSE6 81i5Bt6epnjNxvI1xSwC2LrKvbWeyL9fJKFLI8wW2rDzh5dDwUaBwF7pY4H/8aJQAGpU R55w== X-Gm-Message-State: APjAAAUlvk1JIaEqRWcjjCs+VMu0nylbgJnkDprWSuR3SZpFQWSJgYr5 lghc0GiBx36bZsbkNeDVe3J0+LXGg5Y= X-Google-Smtp-Source: APXvYqwn/wTJt8p+PuqGYx7YYCzZyxsT5ZwMQNjlbn4FMnuwgXauUwZBRMlrQ25Gm7MW5C+8kJe+sQ== X-Received: by 2002:a1c:a904:: with SMTP id s4mr16653129wme.92.1558348498438; Mon, 20 May 2019 03:34:58 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:ac04:eef9:b257:b844? ([2001:b07:6468:f312:ac04:eef9:b257:b844]) by smtp.gmail.com with ESMTPSA id x6sm25589007wru.36.2019.05.20.03.34.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 May 2019 03:34:57 -0700 (PDT) Subject: Re: [PATCH RESEND 2/4] KVM: X86: Emulate MSR_IA32_MISC_ENABLE MWAIT bit To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Sean Christopherson , Liran Alon , Konrad Rzeszutek Wilk References: <1558082990-7822-1-git-send-email-wanpengli@tencent.com> <1558082990-7822-2-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: Date: Mon, 20 May 2019 12:34:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <1558082990-7822-2-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/05/19 10:49, Wanpeng Li wrote: > MSR IA32_MSIC_ENABLE bit 18, according to SDM: > > | When this bit is set to 0, the MONITOR feature flag is not set (CPUID.01H:ECX[bit 3] = 0). > | This indicates that MONITOR/MWAIT are not supported. > | > | Software attempts to execute MONITOR/MWAIT will cause #UD when this bit is 0. > | > | When this bit is set to 1 (default), MONITOR/MWAIT are supported (CPUID.01H:ECX[bit 3] = 1). > > The CPUID.01H:ECX[bit 3] ought to mirror the value of the MSR bit, > CPUID.01H:ECX[bit 3] is a better guard than kvm_mwait_in_guest(). > kvm_mwait_in_guest() affects the behavior of MONITOR/MWAIT, not its > guest visibility. > > This patch implements toggling of the CPUID bit based on guest writes > to the MSR. Won't this disable mwait after migration, unless IA32_MISC_ENABLE is set correctly by firmware or userspace? I think you need to hide this behind KVM_CAP_DISABLE_QUIRKS. (Also, what is the reason for this change in general besides making behavior closer to real hardware?) Thanks, Paolo