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=-5.3 required=3.0 tests=BAYES_00, 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 59D54C07E9C for ; Tue, 6 Jul 2021 04:49:23 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 946DD6198B for ; Tue, 6 Jul 2021 04:49:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 946DD6198B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4GJqpT13QYz303x for ; Tue, 6 Jul 2021 14:49:21 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=verein.lst.de; envelope-from=hch@lst.de; receiver=) Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4GJqp173zYz2yNl for ; Tue, 6 Jul 2021 14:48:56 +1000 (AEST) Received: by verein.lst.de (Postfix, from userid 2407) id 25C5068BEB; Tue, 6 Jul 2021 06:48:49 +0200 (CEST) Date: Tue, 6 Jul 2021 06:48:48 +0200 From: Christoph Hellwig To: Will Deacon Subject: Re: [PATCH v15 06/12] swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing Message-ID: <20210706044848.GA13640@lst.de> References: <20210630114348.GA8383@willie-the-truck> <20210701074045.GA9436@willie-the-truck> <20210702135856.GB11132@willie-the-truck> <0f7bd903-e309-94a0-21d7-f0e8e9546018@arm.com> <20210705190352.GA19461@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210705190352.GA19461@willie-the-truck> User-Agent: Mutt/1.5.17 (2007-11-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: heikki.krogerus@linux.intel.com, thomas.hellstrom@linux.intel.com, peterz@infradead.org, joonas.lahtinen@linux.intel.com, dri-devel@lists.freedesktop.org, chris@chris-wilson.co.uk, grant.likely@arm.com, paulus@samba.org, Frank Rowand , mingo@kernel.org, Marek Szyprowski , Stefano Stabellini , Saravana Kannan , Joerg Roedel , "Rafael J . Wysocki" , Christoph Hellwig , Bartosz Golaszewski , bskeggs@redhat.com, linux-pci@vger.kernel.org, xen-devel@lists.xenproject.org, Thierry Reding , intel-gfx@lists.freedesktop.org, matthew.auld@intel.com, linux-devicetree , Jianxiong Gao , Daniel Vetter , Konrad Rzeszutek Wilk , maarten.lankhorst@linux.intel.com, airlied@linux.ie, Dan Williams , linuxppc-dev@lists.ozlabs.org, jani.nikula@linux.intel.com, Nathan Chancellor , Rob Herring , rodrigo.vivi@intel.com, Bjorn Helgaas , Claire Chang , boris.ostrovsky@oracle.com, Andy Shevchenko , jgross@suse.com, Nicolas Boichat , Greg KH , Randy Dunlap , Qian Cai , lkml , Tomasz Figa , "list@263.net:IOMMU DRIVERS" , Jim Quinlan , xypron.glpk@gmx.de, Tom Lendacky , Robin Murphy , bauerman@linux.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Jul 05, 2021 at 08:03:52PM +0100, Will Deacon wrote: > So at this point, the AMD IOMMU driver does: > > swiotlb = (iommu_default_passthrough() || sme_me_mask) ? 1 : 0; > > where 'swiotlb' is a global variable indicating whether or not swiotlb > is in use. It's picked up a bit later on by pci_swiotlb_late_init(), which > will call swiotlb_exit() if 'swiotlb' is false. > > Now, that used to work fine, because swiotlb_exit() clears > 'io_tlb_default_mem' to NULL, but now with the restricted DMA changes, I > think that all the devices which have successfully probed beforehand will > have stale pointers to the freed structure in their 'dev->dma_io_tlb_mem' > field. Yeah. I don't think we can do that anymore, and I also think it is a bad idea to start with.