Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755036AbYAYJR4 (ORCPT ); Fri, 25 Jan 2008 04:17:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757188AbYAYJRd (ORCPT ); Fri, 25 Jan 2008 04:17:33 -0500 Received: from public.id2-vpn.continvity.gns.novell.com ([195.33.99.129]:7939 "EHLO public.id2-vpn.continvity.gns.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756152AbYAYJR3 convert rfc822-to-8bit (ORCPT ); Fri, 25 Jan 2008 04:17:29 -0500 Message-Id: <4799B75C.76E4.0078.0@novell.com> X-Mailer: Novell GroupWise Internet Agent 7.0.2 HP Date: Fri, 25 Jan 2008 09:18:04 +0000 From: "Jan Beulich" To: "Nick Piggin" Cc: "Keir Fraser" , "Ingo Molnar" , "Harvey Harrison" , "Jeremy Fitzhardinge" , "Matt Mackall" , "Andi Kleen" , "Linux Kernel Mailing List" Subject: Re: [PATCH UPDATE] x86: ignore spurious faults References: <47992CB2.8050606@goop.org> <4799A8A6.76E4.0078.0@novell.com> <200801251938.39231.nickpiggin@yahoo.com.au> In-Reply-To: <200801251938.39231.nickpiggin@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1120 Lines: 24 >>> Nick Piggin 25.01.08 09:38 >>> >On Friday 25 January 2008 19:15, Jan Beulich wrote: >> Actually, another thought: permitting (and handling) spurious faults for >> kernel mappings conflicts with NMI handling, i.e. great care would be >> needed to ensure the NMI path cannot touch any such mapping. So >> even the present Xen/Linux Dom0 implementation may have some >> (perhaps unlikely) problems here, and it would get worse if we added >> e.g. a virtual watchdog NMI (something I am considering, which would >> then extend the problem to DomU-s). > >Can you explain how they conflict? In the same way as vmalloc faults do (which is why vmalloc_sync_all() got introduced): a page fault nested inside an NMI will, by virtue of executing IRET, prematurely tell the processor that NMI handling is done (and specifically unmask further NMIs). Jan -- 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/