Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030249AbWJCCek (ORCPT ); Mon, 2 Oct 2006 22:34:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030250AbWJCCek (ORCPT ); Mon, 2 Oct 2006 22:34:40 -0400 Received: from smtp.osdl.org ([65.172.181.4]:65454 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1030249AbWJCCej (ORCPT ); Mon, 2 Oct 2006 22:34:39 -0400 Date: Mon, 2 Oct 2006 19:34:27 -0700 (PDT) From: Linus Torvalds To: Randy Dunlap cc: akpm , Jesper Juhl , Andi Kleen , Linux Kernel Mailing List Subject: Re: [PATCH/RFC] Math-emu kills the kernel on Athlon64 X2 In-Reply-To: <20061002191638.093fde85.rdunlap@xenotime.net> Message-ID: References: <9a8748490609181518j2d12e4f0l2c55e755e40d38c2@mail.gmail.com> <9a8748490609191414m6748f2fu521637df29ef9e8e@mail.gmail.com> <20061002191638.093fde85.rdunlap@xenotime.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1341 Lines: 33 On Mon, 2 Oct 2006, Randy Dunlap wrote: > > I had no trouble reproducing the boot failure (on Pentium-M), then > I tried TRACE_RESUME(). Nifty, but not really needed here since > earlyprintk worked and contained the fault messages: > > [ 16.841784] math_emulate: 0060:c01062dd > [ 16.845579] Kernel panic - not syncing: Math emulation needed in kernel > > But CONFIG_MATH_EMULATION=y, so what now? The "Math emulation needed in kernel" message means that it was asked to emulate a kernel instruction, and it refuses to do so. The emulation is _not_ meant to be a real FPU, it simply looks like one to user space. A lot of things aren't really emulated (there's no global x87 context, for example: the context is all strictly per-process). > Linus mentioned CPU feature bits. The message log above didn't > make me feel good about them. Sure enough, we are playing with > features before reading the feature bits. Please look up address c01062dd in the system map (or just using gdb), that will tell you what code _tried_ to use the math coprocessor in kernel space. Linus - 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/