From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752386AbaHSLCm (ORCPT ); Tue, 19 Aug 2014 07:02:42 -0400 Received: from 8bytes.org ([81.169.241.247]:43805 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbaHSLCl (ORCPT ); Tue, 19 Aug 2014 07:02:41 -0400 Date: Tue, 19 Aug 2014 13:02:39 +0200 From: Joerg Roedel To: "Li, Zhen-Hua" Cc: David Woodhouse , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/1] iommu/vt-d : clear old root entry for dump kernel Message-ID: <20140819110239.GA16329@8bytes.org> References: <1408352352-14449-1-git-send-email-zhen-hual@hp.com> <1267BB84A242B24E81E0C0C8955CFFC061A4BA26@G9W0343.americas.hpqcorp.net> <20140818232328.GK9809@8bytes.org> <1267BB84A242B24E81E0C0C8955CFFC061A4CA69@G9W0343.americas.hpqcorp.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1267BB84A242B24E81E0C0C8955CFFC061A4CA69@G9W0343.americas.hpqcorp.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 18, 2014 at 11:27:01PM +0000, Li, Zhen-Hua wrote: > : [fault reason 01] Present bit in root entry is clear > It appears when iommu initializing in the kdump kernel. Hmm, do you have an explanation how this can happen? From how I read the code, the kdump kernel disables translation on the IOMMU, then sets a new root entry, and then re-enabled translation. To me it looks like there is no point in time where translation is enabled and the root-entry is clear (present-bit==0). But obviously I am missing something if you see the message above. Btw, have you looked into this patch-set posted earlier this year: https://lkml.org/lkml/2014/4/24/836 It approaches the same problem-space, but also cares about in-flight DMA. Joerg