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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 412A9C54FCB for ; Fri, 24 Apr 2020 16:30:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19A512063A for ; Fri, 24 Apr 2020 16:30:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="G+hOnUfo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728119AbgDXQa0 (ORCPT ); Fri, 24 Apr 2020 12:30:26 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:41501 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726908AbgDXQaZ (ORCPT ); Fri, 24 Apr 2020 12:30:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587745824; 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=lEnOw8ZF0dGRt/O1mfiDTUYS411MyNzBKC0AjVmnO9I=; b=G+hOnUfovzQugdMDvru5Qg7r+uHk9bbdTcdydl0YHwe0aiwHwPAk77lRt7xOOMcG1ef1OO OVBGLETAubzoPTmNNIbJ3GFkDXMxaYgrFTtcfayBK1eCgSXW7ptsnZxKrpLPZK5GQsUdGA jSkjuAvejN98SlV67AzVbl4CbNpS0z8= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-245-VnFJit_1PBWwAEjVk5G7Rw-1; Fri, 24 Apr 2020 12:30:22 -0400 X-MC-Unique: VnFJit_1PBWwAEjVk5G7Rw-1 Received: by mail-wr1-f72.google.com with SMTP id f2so5054767wrm.9 for ; Fri, 24 Apr 2020 09:30:22 -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=lEnOw8ZF0dGRt/O1mfiDTUYS411MyNzBKC0AjVmnO9I=; b=G/VeLH4Jeg/PJogMOg3HiiIWnRRJIVh39DVx2x+NzphnWgKuRXQV9z2ZyHwyJwOL7B VqD1iV1GU7XoxOlTrY8fW8TtihrXbk98zYj7UKDaU3LGeEhYKwFnJf7X4CdTUoEr+dxu JVog4k2aaAV782CCDYb0Om0R2F5zgAGqQTiiiHotKsa9FvBv4FjqvQDeleuhITFurITq 160D4lVIQ+qV3yhepcunSN659QfXakfoEwglBveLGNmcLc9DSEvCKjbL4bOFxCGIdXKy H8+eikx+CGVHaGp0XJ4hleS4o6e0ViZg0A7pNdffSTzdmcirU0PQXw/MSv2wQ9SS2vnM RZiA== X-Gm-Message-State: AGi0PuZVC94ca6wa4KbRI0m7v1q+j+Y9LsWg7ozaLlCtJLSlsqNNn7uQ pUqs7LNH8GWaIghZpO3tdtqtYhm+0e56sdFSLL3b3oVQUaoe+W9MMzcAtosFH43a3BxtAbhxR+1 13TzZVzmlOY4HK70xfmqsNbYr X-Received: by 2002:a1c:384:: with SMTP id 126mr11132862wmd.58.1587745821309; Fri, 24 Apr 2020 09:30:21 -0700 (PDT) X-Google-Smtp-Source: APiQypI5NdM9wUQZ0z948a+KAa0g9t1ym4JE3AZg1fAUjiERTIDRj8cTkPnrs2IYfdntnT5DXIT3Mg== X-Received: by 2002:a1c:384:: with SMTP id 126mr11132840wmd.58.1587745821093; Fri, 24 Apr 2020 09:30:21 -0700 (PDT) Received: from [192.168.10.150] ([93.56.170.5]) by smtp.gmail.com with ESMTPSA id k14sm9205034wrp.53.2020.04.24.09.30.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Apr 2020 09:30:20 -0700 (PDT) Subject: Re: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers To: Jim Mattson , Sean Christopherson Cc: Peter Zijlstra , Li RongQing , LKML , kvm list , the arch/x86 maintainers , "H . Peter Anvin" , Borislav Petkov , Ingo Molnar , Thomas Gleixner , Joerg Roedel , Wanpeng Li , Vitaly Kuznetsov References: <1587704935-30960-1-git-send-email-lirongqing@baidu.com> <20200424100143.GZ20730@hirez.programming.kicks-ass.net> <20200424144625.GB30013@linux.intel.com> From: Paolo Bonzini Message-ID: Date: Fri, 24 Apr 2020 18:30:18 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: 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 24/04/20 18:25, Jim Mattson wrote: >> Assuming we're going forward with this, at an absolute minimum the RDMSRs >> need to be wrapped with checks on host _and_ guest support for the emulated >> behavior. Given the significant overhead, this might even be something >> that should require an extra opt-in from userspace to enable. > > I would like to see performance data before enabling this unconditionally. I wouldn't want this to be enabled unconditionally anyway, because you need to take into account live migration to and from processors that do not have APERF/MPERF support. Paolo