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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 95B14C3A59F for ; Thu, 29 Aug 2019 07:58:28 +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 61BE2205C9 for ; Thu, 29 Aug 2019 07:58:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 61BE2205C9 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 1BED54576; Thu, 29 Aug 2019 07:58:28 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 13754428A for ; Thu, 29 Aug 2019 07:58:15 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id A8690E6 for ; Thu, 29 Aug 2019 07:58:14 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Aug 2019 00:58:14 -0700 X-IronPort-AV: E=Sophos;i="5.64,442,1559545200"; d="scan'208";a="171821817" Received: from jkrzyszt-desk.igk.intel.com (HELO jkrzyszt-desk.ger.corp.intel.com) ([172.22.244.17]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Aug 2019 00:58:12 -0700 From: Janusz Krzysztofik To: Lu Baolu Subject: Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug Date: Thu, 29 Aug 2019 09:58:05 +0200 Message-ID: <3255251.C7nBVfOIaa@jkrzyszt-desk.ger.corp.intel.com> Organization: Intel Technology Poland sp. z o.o. - ul. Slowackiego 173, 80-298 Gdansk - KRS 101882 - NIP 957-07-52-316 In-Reply-To: <0cf4e930-1132-1e7f-815b-57a08a1fe5de@linux.intel.com> 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> MIME-Version: 1.0 Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, David Woodhouse , intel-gfx@lists.freedesktop.org, =?utf-8?B?TWljaGHFgg==?= Wajdeczko 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org 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. 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? Thanks, Janusz > > Thanks, > > Janusz > > Best regards, > Baolu > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu