Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758238AbaD2QTi (ORCPT ); Tue, 29 Apr 2014 12:19:38 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.226]:55517 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758212AbaD2QTg (ORCPT ); Tue, 29 Apr 2014 12:19:36 -0400 Date: Tue, 29 Apr 2014 12:19:34 -0400 From: Steven Rostedt To: Jiri Kosina Cc: "H. Peter Anvin" , Linus Torvalds , linux-kernel@vger.kernel.org, x86@kernel.org, Salman Qazi , Ingo Molnar , Michal Hocko , Borislav Petkov , Vojtech Pavlik , Petr Tesarik , Petr Mladek Subject: Re: 64bit x86: NMI nesting still buggy? Message-ID: <20140429121934.00ea4a2f@gandalf.local.home> In-Reply-To: <20140429120908.61ee947f@gandalf.local.home> References: <20140429100345.3f76a5bd@gandalf.local.home> <20140429120908.61ee947f@gandalf.local.home> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Apr 2014 12:09:08 -0400 Steven Rostedt wrote: > Can you reproduce your problem on different platforms, or is this just > one box that exhibits this behavior? If it's only one box, I'm betting > it has a BIOS doing nasty things. This box probably crashes on all kernels too. My NMI nesting changes did not fix a bug (well, it did as a side effect, see below). It was done to allow NMIs to use IRET so that we could remove stopmachine from ftrace, and instead have it use breakpoints (which return with IRET). The bug that was fixed by this was the ability to do stack traces (sysrq-t) from NMI context. Stack traces can page fault, and when I was debugging hard lock ups and having the NMI do a stack dump of all tasks, another NMI would trigger and corrupt the stack of the NMI doing the dumps. But that was something that would only be seen while debugging, and not something seen in normal operation. I don't see a bug to fix in the kernel. I see a bug to fix in the vendor's BIOS. -- Steve -- 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/