Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757251Ab2BMQvD (ORCPT ); Mon, 13 Feb 2012 11:51:03 -0500 Received: from mail-gy0-f174.google.com ([209.85.160.174]:49103 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757018Ab2BMQvA convert rfc822-to-8bit (ORCPT ); Mon, 13 Feb 2012 11:51:00 -0500 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 13 Feb 2012 08:51:00 -0800 X-Google-Sender-Auth: cGL--GRlsz1hXu4L_Bo_SlS7ZZ0 Message-ID: Subject: Re: [tip:x86/debug] x86/kdump: No need to disable ioapic/ lapic in crash path From: Yinghai Lu To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, torvalds@linux-foundation.org, kexec@lists.infradead.org, vgoyal@redhat.com, akpm@linux-foundation.org, tglx@linutronix.de, dzickus@redhat.com, mingo@elte.hu, linux-tip-commits@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2280 Lines: 69 On Mon, Feb 13, 2012 at 4:52 AM, Eric W. Biederman wrote: > Yinghai Lu writes: > >> On Sat, Feb 11, 2012 at 7:13 PM, Eric W. Biederman >> wrote: >>> Yinghai Lu writes: >>>> After reverting this commit, kdump is working again. >>>> >>>> So assume you need to drop this patch. >>> >>> It sounds like there is a bug in ioapic initialization in the context of >>> VT-d. ?Where do you fail? >>> >> before get debug print out from second kernel, the system get reset. > > Ouch. > > Don can you work with with Yinghai to figure out what is different > between your test configuration and his? > > YH did you have early printk enabled? yes. I always have "console=uart8250,io,0x3f8,115200n8" appended. also i have local patches that print info from arch/x86/boot/compressed/misc.c::decompress_kernel() and arch/x86/kernel/head64.c::x86_64_start_kernel() > > YH Did I understand you properly that things work if you don't enable > VT-d? that is default setting for BIOS and OS. will check if disable that will help. > By VT-d are you referring to interrupt remapping? yes, include interrupt rempapping and dma remapping. > > For anyone watching. ?The premise of this patch was that we can boot > the kernel without resorting to legacy tricks that require us to > put the interrupt controllers in PIT mode. > > Apparently there is some weird corner case that YH can reproduce that > Don did not have in his test set that YH does that causes things to > fail. > > I really don't see any likely candidates when looking at the code. ?The > most I can see is some code that we don't run when interrupt remapping > is enabled in disable_IO_APIC. > > So I suspect we have a bug in our apic initialization somewhere, but > apic initialization should happen after printk are enabled. ?Or at least > after early printks so the reset YH is reporting doesn't make much sense. will try Don's first version patch that only removing disable_IO_APIC. Yinghai -- 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/