From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from g4t3425.houston.hp.com ([15.201.208.53]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XeKDe-0007Q1-OE for kexec@lists.infradead.org; Wed, 15 Oct 2014 08:46:07 +0000 Message-ID: <543E3427.2040207@hp.com> Date: Wed, 15 Oct 2014 16:45:27 +0800 From: "Li, ZhenHua" MIME-Version: 1.0 Subject: Re: [PATCH 0/8] iommu/vt-d: Fix crash dump failure caused by legacy DMA/IO References: <1398386198-19304-1-git-send-email-bill.sumner@hp.com> <1398854973.12733.23.camel@i7.infradead.org> <20140702133258.GN26537@8bytes.org> <20140711162745.GA8335@anatevka.fc.hp.com> <543E2BDA.8030906@hp.com> In-Reply-To: <543E2BDA.8030906@hp.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Joerg Roedel , David Woodhouse Cc: indou.takao@jp.fujitsu.com, bhe@redhat.com, "Vaden, Tom L (HP Server OS Architecture)" , linux-pci@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Jerry.Hoemann@hp.com, iommu@lists.linux-foundation.org, ishii.hironobu@jp.fujitsu.com, bhelgaas@google.com, zhenhua@hp.com Add Tom to CC list. On 10/15/2014 04:10 PM, Li, ZhenHua wrote: > David, Joerg, > I plan to merge this patch set with 3.17 stable kernel, and split this > patch set into two : > 1. The core part, including the changed functions, like [Patch 4/8], > [Patch 8/8]. > 2. For the formatting issues, like [Patch 1/8],[Patch 3/8], including > the changes for code formations, creation of new files > intel-iommu-kdump.c, intel-iommu-private.h. > > I believe this will make the patch set more clear to read and understand. > > What are your suggestions? > > Thanks > Zhenhua > > > On 07/12/2014 12:27 AM, Jerry Hoemann wrote: >> On Wed, Jul 02, 2014 at 03:32:59PM +0200, Joerg Roedel wrote: >>> Hi David, >>> >>> On Wed, Apr 30, 2014 at 11:49:33AM +0100, David Woodhouse wrote: >>>> There could be all kinds of existing mappings in the DMA page tables, >>>> and I'm not sure it's safe to preserve them. What prevents the >>>> crashdump >>>> kernel from trying to use any of the physical pages which are >>>> accessible, and which could thus be corrupted by stray DMA? >>>> >>>> In fact, the old kernel could even have set up 1:1 passthrough mappings >>>> for some devices, which would then be able to DMA *anywhere*. Surely we >>>> need to prevent that? >>> >>> Ideally we would prevent that, yes. But the problem is that a failed DMA >>> transaction might put the device into an unrecoverable state. Usually >>> any in-flight DMA transactions should only target buffers set up by the >>> previous kernel and not corrupt any data. >>> >>>> After the last round of this patchset, we discussed a potential >>>> improvement where you point every virtual bus address at the *same* >>>> physical scratch page. >>> >>> That is a solution to prevent the in-flight DMA failures. But what >>> happens when there is some in-flight DMA to a disk to write some inodes >>> or a new superblock. Then this scratch address-space may cause >>> filesystem corruption at worst. >>> >>> So with this in mind I would prefer initially taking over the >>> page-tables from the old kernel before the device drivers re-initialize >>> the devices. >>> >>> >>> Joerg >> >> David, Joerg, >> >> What do you think here? Do you want me to update the patch set for 3.17? >> >> Jerry >> > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec