From mboxrd@z Thu Jan 1 00:00:00 1970 From: Baoquan He Subject: Re: Kdump kernel hang when set amd_iommu=off Date: Wed, 14 Feb 2018 18:07:05 +0800 Message-ID: <20180214100705.GC28659@localhost.localdomain> References: <20180126080622.GC1759@localhost.localdomain> <20180213132520.nqn5osmgsubzjzcq@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180213132520.nqn5osmgsubzjzcq-zLv9SwRftAIdnm+yROfE0A@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: Joerg Roedel Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi Joerg, On 02/13/18 at 02:25pm, Joerg Roedel wrote: > Hi Baoquan, > > On Fri, Jan 26, 2018 at 04:06:22PM +0800, Baoquan He wrote: > > Saw Huawei's bug report about kdump kernel hang when intel_iommu=off > > is set. I met the similar problem in amd system, only set amd_iommu=off > > in kdump kernel, it means amd_iommu is on in 1st kernel. > > > > I am reading doc and code, trying to debug. Please help have a look when > > convenient, see if there's hint or direction. > > Yeah, I know that this is broken on the AMD-IOMMU side. Problem is that > the IOMMU hardware needs to be disabled in the kdump kernel when > amd_iommu=off is on the command-line. I'll look into fixing that. Thanks for looking into this. This was found by our QE, I checked, and found it only happened on two HPE systems. Other AMD systems have no such issue. Since it's not a blocker, I just go to fix those urgent bugs. > > I thought we fixed this a while ago already for VT-d, is it broken > again? It's not seen in redhat's test machines, just saw Huawei engineers reported this issue. They cc-ed lkml. Thanks Baoquan