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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 45DF4C3A59F for ; Thu, 29 Aug 2019 09:09:57 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 160752073F for ; Thu, 29 Aug 2019 09:09:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 160752073F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id B9B2645E0; Thu, 29 Aug 2019 09:09:56 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id AC6F1459B for ; Thu, 29 Aug 2019 09:09:38 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 1A5E3EC for ; Thu, 29 Aug 2019 09:09:38 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga106.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 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-Language: en-US Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, =?UTF-8?Q?Micha=c5=82_Wajdeczko?= , David Woodhouse , intel-gfx@lists.freedesktop.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.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 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu