From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753300Ab3AYWPk (ORCPT ); Fri, 25 Jan 2013 17:15:40 -0500 Received: from terminus.zytor.com ([198.137.202.10]:47264 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753047Ab3AYWPi (ORCPT ); Fri, 25 Jan 2013 17:15:38 -0500 Message-ID: <510303F8.1080105@zytor.com> Date: Fri, 25 Jan 2013 14:15:20 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: "H. Peter Anvin" CC: mingo@kernel.org, linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, torvalds@linux-foundation.org, JBeulich@suse.com, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:x86/asm] x86/xor: Make virtualization friendly References: <5093E4F302000078000A6162@nat28.tlf.novell.com> <510302FD.3090009@zytor.com> In-Reply-To: <510302FD.3090009@zytor.com> X-Enigmail-Version: 1.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/25/2013 02:11 PM, H. Peter Anvin wrote: > On 01/25/2013 02:43 AM, tip-bot for Jan Beulich wrote: >> Commit-ID: 05fbf4d6fc6a3c0c3e63b77979c9311596716d10 >> Gitweb: http://git.kernel.org/tip/05fbf4d6fc6a3c0c3e63b77979c9311596716d10 >> Author: Jan Beulich >> AuthorDate: Fri, 2 Nov 2012 14:21:23 +0000 >> Committer: Ingo Molnar >> CommitDate: Fri, 25 Jan 2013 09:23:51 +0100 >> >> x86/xor: Make virtualization friendly >> >> In virtualized environments, the CR0.TS management needed here >> can be a lot slower than anticipated by the original authors of >> this code, which particularly means that in such cases forcing >> the use of SSE- (or MMX-) based implementations is not desirable >> - actual measurements should always be done in that case. >> >> For consistency, pull into the shared (32- and 64-bit) header >> not only the inclusion of the generic code, but also that of the >> AVX variants. >> > > This patch is wrong and should be dropped. I verified it with the KVM > people that they do NOT want this change. It is a Xen-specific problem. > FWIW: I have dropped this patch from tip:x86/asm. -hpa