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 CE516C07E96 for ; Tue, 6 Jul 2021 04:48:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B15A86198B for ; Tue, 6 Jul 2021 04:48:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229956AbhGFEvd (ORCPT ); Tue, 6 Jul 2021 00:51:33 -0400 Received: from verein.lst.de ([213.95.11.211]:59053 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229950AbhGFEvd (ORCPT ); Tue, 6 Jul 2021 00:51:33 -0400 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 Cc: Nathan Chancellor , Robin Murphy , Claire Chang , Rob Herring , mpe@ellerman.id.au, Joerg Roedel , Frank Rowand , Konrad Rzeszutek Wilk , boris.ostrovsky@oracle.com, jgross@suse.com, Christoph Hellwig , Marek Szyprowski , benh@kernel.crashing.org, paulus@samba.org, "list@263.net:IOMMU DRIVERS" , Stefano Stabellini , grant.likely@arm.com, xypron.glpk@gmx.de, Thierry Reding , mingo@kernel.org, bauerman@linux.ibm.com, peterz@infradead.org, Greg KH , Saravana Kannan , "Rafael J . Wysocki" , heikki.krogerus@linux.intel.com, Andy Shevchenko , Randy Dunlap , Dan Williams , Bartosz Golaszewski , linux-devicetree , lkml , linuxppc-dev@lists.ozlabs.org, xen-devel@lists.xenproject.org, Nicolas Boichat , Jim Quinlan , Tomasz Figa , bskeggs@redhat.com, Bjorn Helgaas , chris@chris-wilson.co.uk, Daniel Vetter , airlied@linux.ie, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, jani.nikula@linux.intel.com, Jianxiong Gao , joonas.lahtinen@linux.intel.com, linux-pci@vger.kernel.org, maarten.lankhorst@linux.intel.com, matthew.auld@intel.com, rodrigo.vivi@intel.com, thomas.hellstrom@linux.intel.com, Tom Lendacky , Qian Cai 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) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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.