From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751617AbaCQEMQ (ORCPT ); Mon, 17 Mar 2014 00:12:16 -0400 Received: from mail.xen.prgmr.com ([71.19.149.6]:57140 "EHLO mail.xen.prgmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751423AbaCQEMP (ORCPT ); Mon, 17 Mar 2014 00:12:15 -0400 Message-ID: <5326761D.5000905@prgmr.com> Date: Sun, 16 Mar 2014 21:12:13 -0700 From: Sarah Newman User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: "H. Peter Anvin" , David Vrabel CC: Suresh Siddha , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, xen-devel@lists.xen.org Subject: Re: [Xen-devel] [PATCHv1] x86: don't schedule when handling #NM exception References: <1394468273-13676-1-git-send-email-david.vrabel@citrix.com> <531DEB11.2070709@zytor.com> <531DF319.6010800@citrix.com> <53266841.6090308@prgmr.com> <1ebfa80c-4a68-4602-bc98-e5d5f0893998@email.android.com> <53266D94.70902@prgmr.com> <53266F56.9030909@zytor.com> In-Reply-To: <53266F56.9030909@zytor.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/16/2014 08:43 PM, H. Peter Anvin wrote: > On 03/16/2014 08:35 PM, Sarah Newman wrote: >> Can you please review my patch first? It's only enabled when absolutely required. > > It doesn't help. It means you're running on Xen, and you will have > processes subjected to random SIGKILL because they happen to touch the > FPU when the atomic pool is low. > > However, there is probably a happy medium: you don't actually need eager > FPU restore, you just need eager FPU *allocation*. We have been > intending to allocate the FPU state at task creation time for eagerfpu, > and Suresh Siddha has already produced such a patch; it just needs some > minor fixups due to an __init failure. > > http://lkml.kernel.org/r/1391325599.6481.5.camel@europa > > In the Xen case we could turn on eager allocation but not eager fpu. In > fact, it might be justified to *always* do eager allocation... Unconditional eager allocation works. Can xen users count on this being included and applied to the stable kernels? Thanks, Sarah