From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751612AbbHQVDr (ORCPT ); Mon, 17 Aug 2015 17:03:47 -0400 Received: from terminus.zytor.com ([198.137.202.10]:53996 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751206AbbHQVDq (ORCPT ); Mon, 17 Aug 2015 17:03:46 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <20150817080143.GA16928@gmail.com> References: <20150814071500.GA2678@gmail.com> <20150817080143.GA16928@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Subject: Re: [GIT PULL] x86 fixes From: "H. Peter Anvin" Date: Mon, 17 Aug 2015 14:03:09 -0700 To: Ingo Molnar , Linus Torvalds CC: Juergen Gross , Andy Lutomirski , Linux Kernel Mailing List , Thomas Gleixner , Peter Zijlstra , Brian Gerst , Denys Vlasenko , Andrew Morton Message-ID: <3E6EDFF2-D7D7-48FD-BA86-73F256B37B7F@zytor.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Let me see when I last treated this... but I thought it was much more recently than that. On August 17, 2015 1:01:43 AM PDT, Ingo Molnar wrote: > >(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 -- Sent from my Android device with K-9 Mail. Please excuse my brevity.