From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754235Ab3CAARa (ORCPT ); Thu, 28 Feb 2013 19:17:30 -0500 Received: from terminus.zytor.com ([198.137.202.10]:42931 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751513Ab3CAAR3 (ORCPT ); Thu, 28 Feb 2013 19:17:29 -0500 Message-ID: <512FF331.5050008@zytor.com> Date: Thu, 28 Feb 2013 16:15:45 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 MIME-Version: 1.0 To: Josh Boyer CC: Borislav Petkov , Boris Ostrovsky , mingo@redhat.com, tglx@linutronix.de, konrad.wilk@oracle.com, rostedt@goodmis.org, gregkh@linuxfoundation.org, samu.kallio@aberdeencloud.com, kraman@redhat.com, xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: [PATCH] mm/x86: Patch out arch_flush_lazy_mmu_mode() when running on bare metal References: <1362092149-32381-1-git-send-email-boris.ostrovsky@oracle.com> <20130228233720.GB17468@pd.tnic> <20130301000539.GA31649@hansolo.jdub.homelinux.org> In-Reply-To: <20130301000539.GA31649@hansolo.jdub.homelinux.org> X-Enigmail-Version: 1.5 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 02/28/2013 04:05 PM, Josh Boyer wrote: > On Fri, Mar 01, 2013 at 12:37:20AM +0100, Borislav Petkov wrote: >> On Thu, Feb 28, 2013 at 05:55:49PM -0500, Boris Ostrovsky wrote: >>> Invoking arch_flush_lazy_mmu_mode() results in calls to >>> preempt_enable()/disable() which may have performance impact. >>> >>> Since lazy MMU is not used on bare metal we can patch away >>> arch_flush_lazy_mmu_mode() so that it is never called in such >>> environment. >>> >>> Signed-off-by: Boris Ostrovsky >> >> Looks straight-forward enough to me. >> >> Acked-by: Borislav Petkov > > I'll try to get someone to test this tomorrow. > Sounds good. I'd like look at this after the merge window close. I'm kind of bothered about having a choice with an oops on PV, a performance regression on native, or putting a pretty complex patch in as a fix, but since we'll be right after -rc1 it is probably reasonable to pick the last option. -hpa