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=DKIM_INVALID,DKIM_SIGNED, 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 95FE7FA372C for ; Fri, 8 Nov 2019 11:03:16 +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 5F22E21924 for ; Fri, 8 Nov 2019 11:03:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="GPUpB2qi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F22E21924 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 37E6713A6; Fri, 8 Nov 2019 11:03:16 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 6709A1389 for ; Fri, 8 Nov 2019 11:03:15 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 209D1EC for ; Fri, 8 Nov 2019 11:03:15 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C72EF206BA; Fri, 8 Nov 2019 11:03:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573210994; bh=J/Gsm5N/mj+ik5tmWzF15ve/593DRKXBLK4N9zKCikI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GPUpB2qieVF3EyX+Obw28FlE6xo23nwE/xykonNN3EZtnaxcpvEFeX+8ufsaXb5th +ksXQteLE30PzN2sUWXuJdcrvuV/YqSRLbHtKk9h1qsPcUG586CeeZJJMYvyQclJah tyoRDGyrsSCcnNRNjplrIRLCVouz6GYQbwN+T1LQ= Date: Fri, 8 Nov 2019 11:03:10 +0000 From: Will Deacon To: Joerg Roedel Subject: Re: [PATCH 5/7] iommu/arm-smmu-v3: Allow building as a module Message-ID: <20191108110310.GC19153@willie-the-truck> References: <20191030145112.19738-1-will@kernel.org> <20191030145112.19738-6-will@kernel.org> <20191030193148.GA8432@8bytes.org> <20191031154247.GB28061@willie-the-truck> <20191105121508.GA3479@8bytes.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191105121508.GA3479@8bytes.org> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Bjorn Helgaas , iommu@lists.linux-foundation.org, Robin Murphy , linux-kernel@vger.kernel.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-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 Joerg, On Tue, Nov 05, 2019 at 01:15:08PM +0100, Joerg Roedel wrote: > 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()? That's probably a sensible starting point, yes. In conjunction with the patch from Jean-Philippe to introduce bus_unset_iommu(), we might have a fighting chance of getting this to work. I'll spin a v2. Thanks! Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu