From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Li, ZhenHua" Subject: Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel Date: Fri, 03 Apr 2015 17:01:42 +0800 Message-ID: <551E56F6.60503@hp.com> 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"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150403084031.GF22579-0VdLhd/A9PldIt/LePPtNh/sF2h8X+2i0E9HWUfgJXw@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Dave Young Cc: bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, tom.vaden-VXdhtT5mjnY@public.gmane.org, rwright-VXdhtT5mjnY@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lisa.mitchell-VXdhtT5mjnY@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, "Li, ZhenHua" , doug.hatch-VXdhtT5mjnY@public.gmane.org, ishii.hironobu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, billsumnerlinux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, li.zhang6-VXdhtT5mjnY@public.gmane.org, dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org List-Id: iommu@lists.linux-foundation.org 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. Thanks Zhenhua On 04/03/2015 04:40 PM, Dave Young wrote: >> To fix this problem, we modifies the behaviors of the intel vt-d in the >> crashdump kernel: >> >> For DMA Remapping: >> 1. To accept the vt-d hardware in an active state, >> 2. Do not disable and re-enable the translation, keep it enabled. >> 3. Use the old root entry table, do not rewrite the RTA register. >> 4. Malloc and use new context entry table, copy data from the old ones that >> used by the old kernel. > > 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. > > Hope I'm wrong though. > > Thanks > Dave > >