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 1YfKTb-0007DQ-QZ for kexec@lists.infradead.org; Tue, 07 Apr 2015 03:47:00 +0000 Date: Tue, 7 Apr 2015 11:46:22 +0800 From: Dave Young Subject: Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel Message-ID: <20150407034622.GB7213@localhost.localdomain> 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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20150405015453.GB1562@dhcp-17-102.nay.redhat.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: Baoquan He Cc: alex.williamson@redhat.com, indou.takao@jp.fujitsu.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, "Li, ZhenHua" , 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 04/05/15 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. Thanks Dave _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec