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,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 6B505C433E1 for ; Mon, 25 May 2020 13:56:56 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 3F9282071A for ; Mon, 25 May 2020 13:56:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3F9282071A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id E7FD9203BE; Mon, 25 May 2020 13:56:55 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id S4wtoGBpJuq9; Mon, 25 May 2020 13:56:53 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id C235520104; Mon, 25 May 2020 13:56:52 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id A2FB6C088D; Mon, 25 May 2020 13:56:52 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id E167FC016F for ; Mon, 25 May 2020 13:56:50 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id DCB83203BE for ; Mon, 25 May 2020 13:56:50 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id DulZ+xd-jwKQ for ; Mon, 25 May 2020 13:56:49 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from theia.8bytes.org (8bytes.org [81.169.241.247]) by silver.osuosl.org (Postfix) with ESMTPS id 2BCB120104 for ; Mon, 25 May 2020 13:56:49 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id 7407A327; Mon, 25 May 2020 15:56:46 +0200 (CEST) Date: Mon, 25 May 2020 15:56:45 +0200 From: Joerg Roedel To: "Prakhya, Sai Praneeth" Subject: Re: [PATCH] iommu: Remove functions that support private domain Message-ID: <20200525135644.GC5221@8bytes.org> References: <20200514131315.GJ18353@8bytes.org> <20200514183233.GO18353@8bytes.org> <20200514195615.GP18353@8bytes.org> <20200515095919.GQ18353@8bytes.org> <9d65b30a-d22e-d566-d740-601f8d638bfd@linux.intel.com> <20200515154616.GY18353@8bytes.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: "iommu@lists.linux-foundation.org" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 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 Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Sun, May 17, 2020 at 08:29:17AM +0000, Prakhya, Sai Praneeth wrote: > iommu_bus_notifier() > -> iommu_release_device() > -> ops->release_device() (Eg: intel_iommu_release_device()) > -> iommu_group_remove_device() > -> mutex_lock() > > But, I added print statements to iommu_bus_notifier() and > iommu_group_remove_device() and noticed that > iommu_group_remove_device() wasn't being called upon modprobe -r > and iommu_probe_device() isn't called upon modprobe > because Calling modprobe is the device driver binding path, the release_device event is called when a device is going away, e.g. on hotunplug or when a VF of a PCI device is released. This could also happen at runtime, and the code needs to protect against that. My suggestion is still to limit runtime-changing of default domains to groups with only one device. The flow would be as follows: 1. device_lock(dev); // Device can't be bound to a driver or hot-removed from now // on. 2. if (device_is_bound_to_some_driver(dev)) goto 6; 3. mutex_lock(&group->mutex); // group of dev 4. Change the default domain 5. mutex_unlock(&group->mutex); 6. device_unlock(dev); This avoids lock inversion and should be safe with regard to hotplug and device driver probing. Regards, Joerg _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu