From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lu Baolu Subject: Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug Date: Mon, 26 Aug 2019 16:29:12 +0800 Message-ID: <790a4a20-7517-fe54-177d-850b9beeb88e@linux.intel.com> References: <20190822142922.31526-1-janusz.krzysztofik@linux.intel.com> <00f1a3a7-7ff6-e9a0-d9de-a177af6fd64b@linux.intel.com> <7536805.yzB8ZXLclH@jkrzyszt-desk.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <7536805.yzB8ZXLclH@jkrzyszt-desk.ger.corp.intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Janusz Krzysztofik Cc: baolu.lu@linux.intel.com, David Woodhouse , Joerg Roedel , iommu@lists.linux-foundation.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, =?UTF-8?Q?Micha=c5=82_Wajdeczko?= List-Id: intel-gfx@lists.freedesktop.org Hi Janusz, On 8/26/19 4:15 PM, Janusz Krzysztofik wrote: > Hi Lu, > > On Friday, August 23, 2019 3:51:11 AM CEST Lu Baolu wrote: >> Hi, >> >> On 8/22/19 10:29 PM, Janusz Krzysztofik wrote: >>> When a perfectly working i915 device is hot unplugged (via sysfs) and >>> hot re-plugged again, its dev->archdata.iommu field is not populated >>> again with an IOMMU pointer. As a result, the device probe fails on >>> DMA mapping error during scratch page setup. >>> >>> It looks like that happens because devices are not detached from their >>> MMUIO bus before they are removed on device unplug. Then, when an >>> already registered device/IOMMU association is identified by the >>> reinstantiated device's bus and function IDs on IOMMU bus re-attach >>> attempt, the device's archdata is not populated with IOMMU information >>> and the bad happens. >>> >>> I'm not sure if this is a proper fix but it works for me so at least it >>> confirms correctness of my analysis results, I believe. So far I >>> haven't been able to identify a good place where the possibly missing >>> IOMMU bus detach on device unplug operation could be added. >> >> Which kernel version are you testing with? Does it contain below commit? >> >> commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4 >> Author: Lu Baolu >> Date: Thu Aug 1 11:14:58 2019 +0800 > > I was using an internal branch based on drm-tip which didn't contain this > commit yet. Fortunately it has been already merged into drm-tip over last > weekend and has effectively fixed the issue. Thanks for testing this. Best regards, Lu Baolu