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=-2.2 required=3.0 tests=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 5F8C5C433E1 for ; Wed, 17 Jun 2020 11:42:07 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3AB5F206D8 for ; Wed, 17 Jun 2020 11:42:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3AB5F206D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jlWRx-0003En-AN; Wed, 17 Jun 2020 11:41:49 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jlWRw-0003Ei-46 for xen-devel@lists.xenproject.org; Wed, 17 Jun 2020 11:41:48 +0000 X-Inumbo-ID: 8400fb94-b08f-11ea-b9cf-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 8400fb94-b08f-11ea-b9cf-12813bfff9fa; Wed, 17 Jun 2020 11:41:43 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 7EAE7AEF6; Wed, 17 Jun 2020 11:41:46 +0000 (UTC) Subject: Re: [PATCH 7/9] x86/hvm: Disable MPX by default To: Andrew Cooper References: <20200615141532.1927-1-andrew.cooper3@citrix.com> <20200615141532.1927-8-andrew.cooper3@citrix.com> <58d7254d-8953-93c4-9eb2-9be45f39bc4e@suse.com> <6898eb94-868c-b706-7cdd-7d54db09c1b0@suse.com> <76fabe81-3f2c-5c48-c2c0-879bc29f4fb7@citrix.com> <356b06c9-b176-8e72-a3bf-2be62f5cbdb5@suse.com> From: Jan Beulich Message-ID: <7d0b514c-7af6-e1b2-4b95-1ab62fe02e1c@suse.com> Date: Wed, 17 Jun 2020 13:41:42 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Xen-devel , Ian Jackson , Paul Durrant , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 17.06.2020 13:28, Andrew Cooper wrote: > We actually have AVX512 disabled by default in XenServer.  The perf > implications of letting 1 guest play with it is very severe. > > Now I think about it, I'm tempted to recommend it moves out of default > generally. Hmm, I'm tempted to ask whether you're kidding. This is the kind of feature that I see no reason at all to move out of default. Imo we shouldn't put in place policy like this - if anything shouldn't be on by default, it should imo be because of limitations in our handling (I've recently revived my UMIP emulation patch, which comes to mind here) or because of uncertainty on some aspects (like is the case for MOVDIR / ENQCMD for example). Anything else should be left to the admins to decide. Jan