From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753232AbbDGJzt (ORCPT ); Tue, 7 Apr 2015 05:55:49 -0400 Received: from g4t3426.houston.hp.com ([15.201.208.54]:34210 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751765AbbDGJzs (ORCPT ); Tue, 7 Apr 2015 05:55:48 -0400 Message-ID: <5523A977.1030707@hp.com> Date: Tue, 07 Apr 2015 17:55:03 +0800 From: "Li, ZhenHua" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Dave Young CC: Baoquan He , dwmw2@infradead.org, indou.takao@jp.fujitsu.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 v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel References: <1426743388-26908-1-git-send-email-zhen-hual@hp.com> <20150403084031.GF22579@dhcp-128-53.nay.redhat.com> <551E56F6.60503@hp.com> <20150403092111.GG22579@dhcp-128-53.nay.redhat.com> <20150405015453.GB1562@dhcp-17-102.nay.redhat.com> <20150407034622.GB7213@localhost.localdomain> <20150407090837.GE7213@localhost.localdomain> In-Reply-To: <20150407090837.GE7213@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/07/2015 05:08 PM, Dave Young wrote: > On 04/07/15 at 11:46am, Dave Young wrote: >> On 04/05/15 at 09:54am, Baoquan He wrote: >>> On 04/03/15 at 05:21pm, Dave Young wrote: >>>> On 04/03/15 at 05:01pm, Li, ZhenHua wrote: >>>>> Hi Dave, >>>>> >>>>> There may be some possibilities that the old iommu data is corrupted by >>>>> some other modules. Currently we do not have a better solution for the >>>>> dmar faults. >>>>> >>>>> But I think when this happens, we need to fix the module that corrupted >>>>> the old iommu data. I once met a similar problem in normal kernel, the >>>>> queue used by the qi_* functions was written again by another module. >>>>> The fix was in that module, not in iommu module. >>>> >>>> It is too late, there will be no chance to save vmcore then. >>>> >>>> Also if it is possible to continue corrupt other area of oldmem because >>>> of using old iommu tables then it will cause more problems. >>>> >>>> So I think the tables at least need some verifycation before being used. >>>> >>> >>> Yes, it's a good thinking anout this and verification is also an >>> interesting idea. kexec/kdump do a sha256 calculation on loaded kernel >>> and then verify this again when panic happens in purgatory. This checks >>> whether any code stomps into region reserved for kexec/kernel and corrupt >>> the loaded kernel. >>> >>> If this is decided to do it should be an enhancement to current >>> patchset but not a approach change. Since this patchset is going very >>> close to point as maintainers expected maybe this can be merged firstly, >>> then think about enhancement. After all without this patchset vt-d often >>> raised error message, hung. >> >> It does not convince me, we should do it right at the beginning instead of >> introduce something wrong. >> >> I wonder why the old dma can not be remap to a specific page in kdump kernel >> so that it will not corrupt more memory. But I may missed something, I will >> looking for old threads and catch up. > > I have read the old discussion, above way was dropped because it could corrupt > filesystem. Apologize about late commenting. > > But current solution sounds bad to me because of using old memory which is not > reliable. > > Thanks > Dave > Seems we do not have a better solution for the dmar faults. But I believe we can find out how to verify the iommu data which is located in old memory. Thanks Zhenhua From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from g4t3426.houston.hp.com ([15.201.208.54]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YfQEt-0007N4-Mn for kexec@lists.infradead.org; Tue, 07 Apr 2015 09:56:12 +0000 Message-ID: <5523A977.1030707@hp.com> Date: Tue, 07 Apr 2015 17:55:03 +0800 From: "Li, ZhenHua" MIME-Version: 1.0 Subject: Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel References: <1426743388-26908-1-git-send-email-zhen-hual@hp.com> <20150403084031.GF22579@dhcp-128-53.nay.redhat.com> <551E56F6.60503@hp.com> <20150403092111.GG22579@dhcp-128-53.nay.redhat.com> <20150405015453.GB1562@dhcp-17-102.nay.redhat.com> <20150407034622.GB7213@localhost.localdomain> <20150407090837.GE7213@localhost.localdomain> In-Reply-To: <20150407090837.GE7213@localhost.localdomain> 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: Dave Young Cc: alex.williamson@redhat.com, indou.takao@jp.fujitsu.com, Baoquan He , 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 04/07/2015 05:08 PM, Dave Young wrote: > On 04/07/15 at 11:46am, Dave Young wrote: >> On 04/05/15 at 09:54am, Baoquan He wrote: >>> On 04/03/15 at 05:21pm, Dave Young wrote: >>>> On 04/03/15 at 05:01pm, Li, ZhenHua wrote: >>>>> Hi Dave, >>>>> >>>>> There may be some possibilities that the old iommu data is corrupted by >>>>> some other modules. Currently we do not have a better solution for the >>>>> dmar faults. >>>>> >>>>> But I think when this happens, we need to fix the module that corrupted >>>>> the old iommu data. I once met a similar problem in normal kernel, the >>>>> queue used by the qi_* functions was written again by another module. >>>>> The fix was in that module, not in iommu module. >>>> >>>> It is too late, there will be no chance to save vmcore then. >>>> >>>> Also if it is possible to continue corrupt other area of oldmem because >>>> of using old iommu tables then it will cause more problems. >>>> >>>> So I think the tables at least need some verifycation before being used. >>>> >>> >>> Yes, it's a good thinking anout this and verification is also an >>> interesting idea. kexec/kdump do a sha256 calculation on loaded kernel >>> and then verify this again when panic happens in purgatory. This checks >>> whether any code stomps into region reserved for kexec/kernel and corrupt >>> the loaded kernel. >>> >>> If this is decided to do it should be an enhancement to current >>> patchset but not a approach change. Since this patchset is going very >>> close to point as maintainers expected maybe this can be merged firstly, >>> then think about enhancement. After all without this patchset vt-d often >>> raised error message, hung. >> >> It does not convince me, we should do it right at the beginning instead of >> introduce something wrong. >> >> I wonder why the old dma can not be remap to a specific page in kdump kernel >> so that it will not corrupt more memory. But I may missed something, I will >> looking for old threads and catch up. > > I have read the old discussion, above way was dropped because it could corrupt > filesystem. Apologize about late commenting. > > But current solution sounds bad to me because of using old memory which is not > reliable. > > Thanks > Dave > Seems we do not have a better solution for the dmar faults. But I believe we can find out how to verify the iommu data which is located in old memory. Thanks Zhenhua _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec