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=-2.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 D7A2FC004C9 for ; Tue, 7 May 2019 17:59:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5CB420825 for ; Tue, 7 May 2019 17:59:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727553AbfEGR7V (ORCPT ); Tue, 7 May 2019 13:59:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:60402 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726545AbfEGR7U (ORCPT ); Tue, 7 May 2019 13:59:20 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CB2C1ABF3; Tue, 7 May 2019 17:59:19 +0000 (UTC) Date: Tue, 7 May 2019 19:59:13 +0200 From: Borislav Petkov To: Linus Torvalds Cc: Rik van Riel , Sebastian Andrzej Siewior , x86-ml , lkml Subject: Re: [GIT PULL] x86 FPU changes for 5.2 Message-ID: <20190507175913.GC26655@zn.tnic> References: <20190507132632.GB26655@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 07, 2019 at 10:35:25AM -0700, Linus Torvalds wrote: > I love this and we should have done it long ago, but I also worry that > every time we've messed with the FP state, we've had interesting bugs. Tell me about it. Our FPU code is one helluva contraption. > Which is obviously why we didn't do this long ago. > > Has this gone through lots of testing, particularly with things like > FP signal handling and old machines that don't necessarily have > anything but the most basic FP state (ie Pentium class etc)? Right, so I ran it on the bunch of boxes I have here, the oldest is a K8 which has: [ 0.000000] x86/fpu: x87 FPU will use FXSAVE and it looked ok. Ingo ran it on his fleet too, AFAIR. Lemme see if I can dig out something older at work. > I've pulled it, but I'd still like to feel safer about it after-the-fact ;) Yeah. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Mary Higgins, Sri Rasiah, HRB 21284 (AG Nürnberg)