From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 036B0C3A59F for ; Thu, 29 Aug 2019 09:09:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D4B552073F for ; Thu, 29 Aug 2019 09:09:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727228AbfH2JJi (ORCPT ); Thu, 29 Aug 2019 05:09:38 -0400 Received: from mga11.intel.com ([192.55.52.93]:1913 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726038AbfH2JJh (ORCPT ); Thu, 29 Aug 2019 05:09:37 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Aug 2019 02:09:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,442,1559545200"; d="scan'208";a="380707285" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by fmsmga005.fm.intel.com with ESMTP; 29 Aug 2019 02:09:36 -0700 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?= Subject: Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug To: Janusz Krzysztofik References: <20190822142922.31526-1-janusz.krzysztofik@linux.intel.com> <3275480.HMaYE7B3nd@jkrzyszt-desk.ger.corp.intel.com> <0cf4e930-1132-1e7f-815b-57a08a1fe5de@linux.intel.com> <3255251.C7nBVfOIaa@jkrzyszt-desk.ger.corp.intel.com> From: Lu Baolu Message-ID: Date: Thu, 29 Aug 2019 17:08:18 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <3255251.C7nBVfOIaa@jkrzyszt-desk.ger.corp.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 8/29/19 3:58 PM, Janusz Krzysztofik wrote: > Hi Baolu, > > On Thursday, August 29, 2019 3:43:31 AM CEST Lu Baolu wrote: >> Hi Janusz, >> >> On 8/28/19 10:17 PM, Janusz Krzysztofik wrote: >>>> We should avoid kernel panic when a intel_unmap() is called against >>>> a non-existent domain. >>> Does that mean you suggest to replace >>> BUG_ON(!domain); >>> with something like >>> if (WARN_ON(!domain)) >>> return; >>> and to not care of orphaned mappings left allocated? Is there a way to > inform >>> users that their active DMA mappings are no longer valid and they > shouldn't >>> call dma_unmap_*()? >>> >>>> But we shouldn't expect the IOMMU driver not >>>> cleaning up the domain info when a device remove notification comes and >>>> wait until all file descriptors being closed, right? >>> Shouldn't then the IOMMU driver take care of cleaning up resources still >>> allocated on device remove before it invalidates and forgets their > pointers? >>> >> >> You are right. We need to wait until all allocated resources (iova and >> mappings) to be released. >> >> How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and >> removing the domain info when the driver detachment completes? > > Device core calls BUS_NOTIFY_UNBOUND_DRIVER on each driver unbind, regardless > of a device being removed or not. As long as the device is not unplugged and > the BUS_NOTIFY_REMOVED_DEVICE notification not generated, an unbound driver is > not a problem here. > Morever, BUS_NOTIFY_UNBOUND_DRIVER is called even before > BUS_NOTIFY_REMOVED_DEVICE so that wouldn't help anyway. > Last but not least, bus events are independent of the IOMMU driver use via > DMA-API it exposes. Fair enough. > > If keeping data for unplugged devices and reusing it on device re-plug is not > acceptable then maybe the IOMMU driver should perform reference counting of > its internal resources occupied by DMA-API users and perform cleanups on last > release? I am not saying that keeping data is not acceptable. I just want to check whether there are any other solutions. Best regards, Baolu