From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v10 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel
Date: Wed, 6 May 2015 10:25:59 +0200
Message-ID: <20150506082559.GC20611@8bytes.org>
References: <552DFB56.1070600@hp.com>
	<20150415064803.GF19051@localhost.localdomain>
	<20150424080147.GC4458@dhcp-16-116.nay.redhat.com>
	<20150424082528.GA23912@dhcp-128-91.nay.redhat.com>
	<20150424083530.GD4458@dhcp-16-116.nay.redhat.com>
	<20150424084957.GC23912@dhcp-128-91.nay.redhat.com>
	<20150504162318.GH15736@8bytes.org>
	<20150505061423.GC31063@dhcp-128-4.nay.redhat.com>
	<20150505153157.GQ15736@8bytes.org>
	<20150506015135.GB14065@dhcp-128-4.nay.redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
Content-Disposition: inline
In-Reply-To: <20150506015135.GB14065-0VdLhd/A9PlTxLCkMk2GaBcY2uh10dtjAL8bYrjMMd8@public.gmane.org>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/iommu>,
	<mailto:iommu-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/iommu/>
List-Post: <mailto:iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
List-Help: <mailto:iommu-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/iommu>,
	<mailto:iommu-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=subscribe>
Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
To: Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Baoquan He <bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, tom.vaden-VXdhtT5mjnY@public.gmane.org, rwright-VXdhtT5mjnY@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lisa.mitchell-VXdhtT5mjnY@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, "Li,
	ZhenHua" <zhen-hual-VXdhtT5mjnY@public.gmane.org>, doug.hatch-VXdhtT5mjnY@public.gmane.org, ishii.hironobu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, billsumnerlinux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, li.zhang6-VXdhtT5mjnY@public.gmane.org, dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
List-Id: iommu@lists.linux-foundation.org

On Wed, May 06, 2015 at 09:51:35AM +0800, Dave Young wrote:
> DMA write will modify system ram, if the old data is corrupted  it is possible
> that DMA operation modify wrong ram regions because of wrong mapping.
> Am I missing something and is it not possible?

This might have happened already before the kdump kernel even boots.
Also, if there is no IOMMU, this can happen as well. This (unlikely
but possible) situation doesn't make things worse.


	Joerg