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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 6D691C83000 for ; Wed, 29 Apr 2020 13:55:56 +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 48D572083B for ; Wed, 29 Apr 2020 13:55:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 48D572083B 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 1jTnBe-0003U0-Ss; Wed, 29 Apr 2020 13:55:42 +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 1jTnBe-0003Tv-48 for xen-devel@lists.xenproject.org; Wed, 29 Apr 2020 13:55:42 +0000 X-Inumbo-ID: 1ce41a16-8a21-11ea-994e-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 1ce41a16-8a21-11ea-994e-12813bfff9fa; Wed, 29 Apr 2020 13:55:41 +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 A898AABBE; Wed, 29 Apr 2020 13:55:39 +0000 (UTC) Subject: Re: [PATCH v2 1/3] x86/pv: Options to disable and/or compile out 32bit PV support To: Andrew Cooper References: <20200417155004.16806-2-andrew.cooper3@citrix.com> <20200429130631.6018-1-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: <6f629cab-e729-5201-3315-130b0a1d3082@suse.com> Date: Wed, 29 Apr 2020 15:55:39 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200429130631.6018-1-andrew.cooper3@citrix.com> 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 , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 29.04.2020 15:06, Andrew Cooper wrote: > This is the start of some performance and security-hardening improvements, > based on the fact that 32bit PV guests are few and far between these days. > > Ring1 is full of architectural corner cases, such as counting as supervisor > from a paging point of view. This accounts for a substantial performance hit > on processors from the last 8 years (adjusting SMEP/SMAP on every privilege > transition), and the gap is only going to get bigger with new hardware > features. > > Signed-off-by: Andrew Cooper > Reviewed-by: Wei Liu > Reviewed-by: Roger Pau Monné Acked-by: Jan Beulich