From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751904AbYIYOHm (ORCPT ); Thu, 25 Sep 2008 10:07:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753010AbYIYOHe (ORCPT ); Thu, 25 Sep 2008 10:07:34 -0400 Received: from rv-out-0506.google.com ([209.85.198.229]:5507 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753185AbYIYOHd (ORCPT ); Thu, 25 Sep 2008 10:07:33 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=L1dnTQ9x2Cxy/kR7RsomyV5XJ9ACxSLsplolpnbjEeDap0Y+yadb1EIoFmRp9/uDhC OZuoSPpSq0osPGX9tfqGKXDHuoqeMEgrti+qkjAsvxzxpB/7NOBu4SB/kza1CEk2L0rj TQEdKiHOgifjeCQtWNKa8GPeSSdqhWsAC5aqo= Message-ID: <19f34abd0809250707i18ded94aib177c884d4d6a3bd@mail.gmail.com> Date: Thu, 25 Sep 2008 16:07:32 +0200 From: "Vegard Nossum" To: "H. Peter Anvin" Subject: Re: v2.6.27-rc7: x86: #GP on panic? Cc: "Ingo Molnar" , x86@kernel.org, linux-kernel@vger.kernel.org, "Thomas Gleixner" In-Reply-To: <48DB5186.8060502@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <19f34abd0809241209l3a69d607v153549ee43e085e9@mail.gmail.com> <20080925080417.GB27048@elte.hu> <48DB5186.8060502@zytor.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 25, 2008 at 10:53 AM, H. Peter Anvin wrote: > Ingo Molnar wrote: >> >> * Vegard Nossum wrote: >> >>> Hi, >>> >>> With 2.6.27-rc7 on qemu-x86_64, it seems that panic will trigger a >>> General Protection Fault. I haven't seen it before. >> >>> [ 4.523641] Code: eb fd 55 48 89 e5 53 51 83 3d 25 e8 78 00 00 75 >>> 1a 31 d2 31 f6 48 c7 c7 e1 9c 01 81 e8 f7 a4 03 00 9c 5b fa e8 94 09 >>> 00 00 53 9d <5a> 5b c9 c3 55 31 c0 48 89 e5 89 04 25 b0 c0 5f ff 65 83 >>> 04 25 >> >> hm, 0x5a is a simple pop %rdx. A #GP there means the stack segment is >> bust? >> > > No, that would be #SS (and segments don't really exist in 64-bit mode > anyway.) In 32-bit mode it could mean a code segment overrun. > > *However*... > > [ 4.523477] general protection fault: fff2 [1] SMP > > There is an error code attached to the #GP, which is supposed to mean that > somehow a segment selector was involved. This doesn't look like a very valid > segment selector at all. > >> hm: >> >>> ffffffff8101a6b9 >>> ffffffff81019d25: 53 push %rbx >>> ffffffff81019d26: 9d popfq >>> ffffffff81019d27: 5a pop %rdx >> >> so it's preceded by a popfq and on the next instruction we #GP. >> >> but the stack and flags state looks good: >> >> [ 4.523641] RSP: 0018:ffff880007867d70 EFLAGS: 00000286 >> > > My guess is that the popfq enables interrupts, and we try to take an > interrupt through an IDT entry which isn't set up correctly. I'm sorry for the false alarm. I discovered that it did not happen on a clean kernel. My kernel was using this patch. diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c index a11f5d4..abf5bc8 100644 --- a/arch/x86/kernel/cpu/common_64.c +++ b/arch/x86/kernel/cpu/common_64.c @@ -261,6 +261,8 @@ void __init early_cpu_init(void) cpu_devs[cvdev->vendor] = cvdev->cpu_dev; early_cpu_support_print(); early_identify_cpu(&boot_cpu_data); + + setup_clear_cpu_cap(X86_FEATURE_PSE); } /* Do some early cpuid on the boot CPU to get some parameter that are :-( Vegard -- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036