From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel Date: Mon, 4 May 2015 13:05:51 +0200 Message-ID: <20150504110551.GD15736@8bytes.org> References: <1426743388-26908-1-git-send-email-zhen-hual@hp.com> <20150403084031.GF22579@dhcp-128-53.nay.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150403084031.GF22579@dhcp-128-53.nay.redhat.com> Sender: linux-pci-owner@vger.kernel.org To: Dave Young Cc: "Li, Zhen-Hua" , dwmw2@infradead.org, indou.takao@jp.fujitsu.com, bhe@redhat.com, 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 List-Id: iommu@lists.linux-foundation.org On Fri, Apr 03, 2015 at 04:40:31PM +0800, Dave Young wrote: > Have not read all the patches, but I have a question, not sure this > has been answered before. Old memory is not reliable, what if the old > memory get corrupted before panic? Is it safe to continue using it in > 2nd kernel, I worry that it will cause problems. Yes, the old memory could be corrupted, and there are more failure cases left which we have no way of handling yet (if iommu data structures are in kdump backup areas). The question is what to do if we find some of the old data structures corrupted, hand how far should the tests go. Should we also check the page-tables, for example? I think if some of the data structures for a device are corrupted it probably already failed in the old kernel and things won't get worse in the new one. So checking is not strictly necessary in the first version of these patches (unless we find a valid failure scenario). Once we have some good plan on what to do if we find corruption, we can add checking of course. Regards, Joerg