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 470D3C010A2 for ; Tue, 5 Nov 2019 12:15:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 238A022480 for ; Tue, 5 Nov 2019 12:15:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730918AbfKEMPR (ORCPT ); Tue, 5 Nov 2019 07:15:17 -0500 Received: from 8bytes.org ([81.169.241.247]:50602 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726524AbfKEMPR (ORCPT ); Tue, 5 Nov 2019 07:15:17 -0500 Received: by theia.8bytes.org (Postfix, from userid 1000) id 1DCFD450; Tue, 5 Nov 2019 13:15:15 +0100 (CET) Date: Tue, 5 Nov 2019 13:15:08 +0100 From: Joerg Roedel To: Will Deacon Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Robin Murphy , Bjorn Helgaas , Lorenzo Pieralisi Subject: Re: [PATCH 5/7] iommu/arm-smmu-v3: Allow building as a module Message-ID: <20191105121508.GA3479@8bytes.org> References: <20191030145112.19738-1-will@kernel.org> <20191030145112.19738-6-will@kernel.org> <20191030193148.GA8432@8bytes.org> <20191031154247.GB28061@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191031154247.GB28061@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Will, On Thu, Oct 31, 2019 at 03:42:47PM +0000, Will Deacon wrote: > Generally, I think unloading the IOMMU driver module while there are > active users is a pretty bad idea, much like unbinding the driver via > /sys in the same situation would also be fairly daft. However, I *think* > the code in __device_release_driver() tries to deal with this by > iterating over the active consumers and ->remove()ing them first. > > I'm without hardware access at the moment, so I haven't been able to > test this myself. We could nobble the module_exit() hook, but there's > still the "force unload" option depending on the .config. Okay, but besides the force-unload case, can we prevent accidential unloading by taking a reference to the module in add_device() and release it in remove_device()? Regards, Joerg