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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2530EC433EF for ; Thu, 14 Oct 2021 11:44:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E71B61156 for ; Thu, 14 Oct 2021 11:44:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231228AbhJNLqp (ORCPT ); Thu, 14 Oct 2021 07:46:45 -0400 Received: from mga05.intel.com ([192.55.52.43]:27262 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231236AbhJNLqm (ORCPT ); Thu, 14 Oct 2021 07:46:42 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10136"; a="313858117" X-IronPort-AV: E=Sophos;i="5.85,372,1624345200"; d="scan'208";a="313858117" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2021 04:44:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.85,372,1624345200"; d="scan'208";a="626772293" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.171]) by fmsmga001.fm.intel.com with SMTP; 14 Oct 2021 04:44:34 -0700 Received: by stinkbox (sSMTP sendmail emulation); Thu, 14 Oct 2021 14:44:33 +0300 Date: Thu, 14 Oct 2021 14:44:33 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Borislav Petkov Cc: Ser Olmy , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [regression] commit d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Patchwork-Hint: comment Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I have a 32bit installation here that stopped working. Bisected it to commit d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits"). dhcpcd was the first thing I notice being affected on account of network not coming up, and after trying to look at it with gdb also gdb turned out to be broken. strace of dhcpcd shows a SIGFPE getting delivered, after which it gets stuck (seem to be sitting in poll but not responding to even ^C). And gdb seems to be stuck in a perpetual SIGFPE loop and won't even get to the prompt. The crucial bit here seems to be that most of the software is built with -mfpmath=sse. After rebuilding dhcpcd without that it started to work on the broken kernel. Rebuilding gdb didn't help so I whatever SSE usage is causing the issue is presumably happening in a library. Had to do the rebuilds on a working kernel as well because otherwise the build itself would die to a SIGFPE somewhere. Tested the same disk on on both a 64bit capable Pentium D and a 32bit only Pentium 4 just to rule out the specific CPU. Busted on both. -- Ville Syrjälä Intel