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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 60104C5CFC1 for ; Tue, 19 Jun 2018 15:02:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 089F4204EC for ; Tue, 19 Jun 2018 15:02:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 089F4204EC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=codethink.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966534AbeFSPCm (ORCPT ); Tue, 19 Jun 2018 11:02:42 -0400 Received: from imap1.codethink.co.uk ([176.9.8.82]:57355 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965681AbeFSPCl (ORCPT ); Tue, 19 Jun 2018 11:02:41 -0400 Received: from [148.252.241.226] (helo=xylophone) by imap1.codethink.co.uk with esmtpsa (Exim 4.84_2 #1 (Debian)) id 1fVI9Q-0003SP-TD; Tue, 19 Jun 2018 16:02:33 +0100 Message-ID: <1529420551.19394.2.camel@codethink.co.uk> Subject: Re: [PATCH 4.4 10/24] x86/fpu: Hard-disable lazy FPU mode From: Ben Hutchings To: Daniel Sangorrin , 'Greg Kroah-Hartman' , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, 'Andy Lutomirski' , 'Rik van Riel' , 'Borislav Petkov' , 'Brian Gerst' , 'Dave Hansen' , 'Denys Vlasenko' , 'Fenghua Yu' , "'H. Peter Anvin'" , 'Josh Poimboeuf' , 'Linus Torvalds' , 'Oleg Nesterov' , 'Peter Zijlstra' , 'Quentin Casasnovas' , 'Thomas Gleixner' , pbonzini@redhat.com, 'Ingo Molnar' Date: Tue, 19 Jun 2018 16:02:31 +0100 In-Reply-To: <000c01d40460$bfc97710$3f5c6530$@toshiba.co.jp> References: <20180614132724.483802160@linuxfoundation.org> <20180614132724.905032027@linuxfoundation.org> <000c01d40460$bfc97710$3f5c6530$@toshiba.co.jp> Organization: Codethink Ltd. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2018-06-15 at 13:24 +0900, Daniel Sangorrin wrote: > Hi Greg, > > >  /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */ > > --- a/arch/x86/include/asm/fpu/internal.h > > +++ b/arch/x86/include/asm/fpu/internal.h > > @@ -58,7 +58,7 @@ extern u64 fpu__get_supported_xfeatures_ > >   */ > >  static __always_inline __pure bool use_eager_fpu(void) > >  { > > - return static_cpu_has_safe(X86_FEATURE_EAGER_FPU); > > + return true; > >  } > > Since this function returns always true then we can remove the code depending on lazy FPU mode. > Actually this has already been done in "x86/fpu: Remove use_eager_fpu()" > Ref: https://patchwork.kernel.org/patch/9365883/ > > >  static void __init fpu__init_parse_early_param(void) > >  { > > - if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off")) { > > - eagerfpu = DISABLE; > > - fpu__clear_eager_fpu_features(); > > - } > > Since this patch removes the kernel boot parameter "eagerfpu", maybe we should remove it from the Documentation. > This has also been done by commit "x86/fpu: Finish excising 'eagerfpu'" > Ref: https://patchwork.kernel.org/patch/9380673/ > > I will try backporting those patches unless anyone has any objections. This does seem like a good idea—there is quite a bit of dead code left and it may be hard to backport any further bug fixes in this area without that removal. Ben. -- Ben Hutchings, Software Developer   Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom