From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756524AbbAPPzw (ORCPT ); Fri, 16 Jan 2015 10:55:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37999 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717AbbAPPzv (ORCPT ); Fri, 16 Jan 2015 10:55:51 -0500 Date: Fri, 16 Jan 2015 16:54:45 +0100 From: Oleg Nesterov To: Rik van Riel Cc: Linus Torvalds , Suresh Siddha , linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, matt.fleming@intel.com, bp@suse.de, pbonzini@redhat.com, tglx@linutronix.de, luto@amacapital.net Subject: Re: [PATCH 2/3] x86, fpu: don't abuse ->has_fpu in __kernel_fpu_{begin,end}() Message-ID: <20150116155445.GA7249@redhat.com> References: <1421012793-30106-1-git-send-email-riel@redhat.com> <20150115191918.GA27332@redhat.com> <20150115192005.GC27332@redhat.com> <54B876FD.3060702@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54B876FD.3060702@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/15, Rik van Riel wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 01/15/2015 02:20 PM, Oleg Nesterov wrote: > > b/arch/x86/kernel/i387.c @@ -81,9 +81,7 @@ void > > __kernel_fpu_begin(void) this_cpu_write(in_kernel_fpu, true); > > > > if (__thread_has_fpu(me)) { - __thread_clear_has_fpu(me); > > I will put that line back in the patch series that defers the > loading of FPU state until the switch to user space, I think this needs more discussion. Firstly, __thread_clear_has_fpu() should go into __kernel_fpu_end(), it should replace restore_fpu_checking(). But does your series actually need this change? Correctness-wise this is not needed (afaics). Performance-wise I am not sure, kernel_fpu_begin() is unlikely event. Plus I am not sure this is a win (in general), but I can be easily wrong. > but I > guess we can go either way for now... Yes, this should not really conflict with your changes in any case. Given that you acked 1/3 and 3/3, perhaps you can ack this one as well? Oleg.