Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754026AbbHQIBv (ORCPT ); Mon, 17 Aug 2015 04:01:51 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:35675 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752105AbbHQIBt (ORCPT ); Mon, 17 Aug 2015 04:01:49 -0400 Date: Mon, 17 Aug 2015 10:01:43 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Juergen Gross , Andy Lutomirski , Linux Kernel Mailing List , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Brian Gerst , Denys Vlasenko , Andrew Morton Subject: Re: [GIT PULL] x86 fixes Message-ID: <20150817080143.GA16928@gmail.com> References: <20150814071500.GA2678@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1934 Lines: 46 (Sorry about the late reply, wasn't around on the weekend.) * Linus Torvalds wrote: > Now that said, I doubt anybody cares. Since we don't support the original 80386, > the only way to ever trigger FP emulation is by having a 486SX or possibly a > couple of even rarer clone chips. [...] Yeah. So when I re-wrote the FPU code I tried to test math-emu by booting with 'no387': it turned out that ever since the XSAVE code got merged upstream, math-emu oopsed reliably during bootup with a NULL reference, because it wasn't updated to the dynamic allocation logic in: 61c4628b5386 ("x86, fpu: split FPU state from task struct - v5") That was 6 years ago, so anything v2.6.26 and later probably has 100% non-working math-emu. So when I re-introduced static allocations math-emu started working again, to a limited degree: on a modern distro, trying to boot /bin/bash I got a prompt, but various programs would segfault. I did not investigate it any deeper, I suppose the FPU emulation does not go far enough for modern user-space, or maybe it has more bugs. So in reality nobody has cared about x86 math-emu in the last 6 years and we can probably remove it for good. I kept it for nostalgic reasons, but I guess using v2.4 kernels ought to be enough for those with nostalgia? > [...] So it's not like the fact that the code is completely wrong and crap > actually *matters*, but I still refuse to pull stuff that seems to be so > completely screwed up. That's true, my bad for merging it! Any objections against removing all of math-emu in v4.3? This would simplify the FPU code in various places beyond math-emu/. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/