From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752200AbbDOGs0 (ORCPT ); Wed, 15 Apr 2015 02:48:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49711 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751146AbbDOGsR (ORCPT ); Wed, 15 Apr 2015 02:48:17 -0400 Date: Wed, 15 Apr 2015 14:48:03 +0800 From: Dave Young To: "Li, ZhenHua" Cc: dwmw2@infradead.org, indou.takao@jp.fujitsu.com, bhe@redhat.com, joro@8bytes.org, vgoyal@redhat.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, kexec@lists.infradead.org, alex.williamson@redhat.com, ddutile@redhat.com, ishii.hironobu@jp.fujitsu.com, bhelgaas@google.com, doug.hatch@hp.com, jerry.hoemann@hp.com, tom.vaden@hp.com, li.zhang6@hp.com, lisa.mitchell@hp.com, billsumnerlinux@gmail.com, rwright@hp.com Subject: Re: [PATCH v10 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel Message-ID: <20150415064803.GF19051@localhost.localdomain> References: <1428655333-19504-1-git-send-email-zhen-hual@hp.com> <20150415005731.GC19051@localhost.localdomain> <552DFB56.1070600@hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <552DFB56.1070600@hp.com> User-Agent: Mutt/1.5.22.1-rc1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/15/15 at 01:47pm, Li, ZhenHua wrote: > On 04/15/2015 08:57 AM, Dave Young wrote: > >Again, I think it is bad to use old page table, below issues need consider: > >1) make sure old page table are reliable across crash > >2) do not allow writing oldmem after crash > > > >Please correct me if I'm wrong, or if above is not doable I think I will vote for > >resetting pci bus. > > > >Thanks > >Dave > > > Hi Dave, > > When updating the context tables, we have to write their address to root > tables, this will cause writing to old mem. > > Resetting the pci bus has been discussed, please check this: > http://lists.infradead.org/pipermail/kexec/2014-October/012752.html > https://lkml.org/lkml/2014/10/21/890 I know one reason to use old pgtable is this looks better because it fixes the real problem, but it is not a good way if it introduce more problems because of it have to use oldmem. I will be glad if this is not a problem but I have not been convinced. OTOH, there's many types of iommu, intel, amd, a lot of other types. They need their own fixes, so it looks not that elegant. For pci reset, it is not perfect, but it has another advantage, the patch is simpler. The problem I see from the old discusssion is, reset bus in 2nd kernel is acceptable but it does not fix things on sparc platform. AFAIK current reported problems are intel and amd iommu, at least pci reset stuff does not make it worse. Thanks Dave From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YiH7m-00012t-Th for kexec@lists.infradead.org; Wed, 15 Apr 2015 06:48:40 +0000 Date: Wed, 15 Apr 2015 14:48:03 +0800 From: Dave Young Subject: Re: [PATCH v10 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel Message-ID: <20150415064803.GF19051@localhost.localdomain> References: <1428655333-19504-1-git-send-email-zhen-hual@hp.com> <20150415005731.GC19051@localhost.localdomain> <552DFB56.1070600@hp.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <552DFB56.1070600@hp.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: "Li, ZhenHua" Cc: alex.williamson@redhat.com, indou.takao@jp.fujitsu.com, bhe@redhat.com, tom.vaden@hp.com, rwright@hp.com, linux-pci@vger.kernel.org, joro@8bytes.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, lisa.mitchell@hp.com, jerry.hoemann@hp.com, iommu@lists.linux-foundation.org, ddutile@redhat.com, doug.hatch@hp.com, ishii.hironobu@jp.fujitsu.com, bhelgaas@google.com, billsumnerlinux@gmail.com, li.zhang6@hp.com, dwmw2@infradead.org, vgoyal@redhat.com On 04/15/15 at 01:47pm, Li, ZhenHua wrote: > On 04/15/2015 08:57 AM, Dave Young wrote: > >Again, I think it is bad to use old page table, below issues need consider: > >1) make sure old page table are reliable across crash > >2) do not allow writing oldmem after crash > > > >Please correct me if I'm wrong, or if above is not doable I think I will vote for > >resetting pci bus. > > > >Thanks > >Dave > > > Hi Dave, > > When updating the context tables, we have to write their address to root > tables, this will cause writing to old mem. > > Resetting the pci bus has been discussed, please check this: > http://lists.infradead.org/pipermail/kexec/2014-October/012752.html > https://lkml.org/lkml/2014/10/21/890 I know one reason to use old pgtable is this looks better because it fixes the real problem, but it is not a good way if it introduce more problems because of it have to use oldmem. I will be glad if this is not a problem but I have not been convinced. OTOH, there's many types of iommu, intel, amd, a lot of other types. They need their own fixes, so it looks not that elegant. For pci reset, it is not perfect, but it has another advantage, the patch is simpler. The problem I see from the old discusssion is, reset bus in 2nd kernel is acceptable but it does not fix things on sparc platform. AFAIK current reported problems are intel and amd iommu, at least pci reset stuff does not make it worse. Thanks Dave _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec