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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 25991C76194 for ; Tue, 23 Jul 2019 15:38:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 06280223BA for ; Tue, 23 Jul 2019 15:38:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388617AbfGWPie (ORCPT ); Tue, 23 Jul 2019 11:38:34 -0400 Received: from verein.lst.de ([213.95.11.211]:42777 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727598AbfGWPid (ORCPT ); Tue, 23 Jul 2019 11:38:33 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id EBAB168B02; Tue, 23 Jul 2019 17:38:30 +0200 (CEST) Date: Tue, 23 Jul 2019 17:38:30 +0200 From: Christoph Hellwig To: "Michael S. Tsirkin" Cc: Eric Auger , eric.auger.pro@gmail.com, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call Message-ID: <20190723153830.GD720@lst.de> References: <20190722145509.1284-1-eric.auger@redhat.com> <20190722145509.1284-3-eric.auger@redhat.com> <20190722112704-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190722112704-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 22, 2019 at 11:33:35AM -0400, Michael S. Tsirkin wrote: > On Mon, Jul 22, 2019 at 04:55:09PM +0200, Eric Auger wrote: > > Do not call dma_max_mapping_size for devices that have no DMA > > mask set, otherwise we can hit a NULL pointer dereference. > > > > This occurs when a virtio-blk-pci device is protected with > > a virtual IOMMU. > > > > Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()") > > Signed-off-by: Eric Auger > > Suggested-by: Christoph Hellwig > > Christoph, I wonder why did you suggest this? > The connection between dma_mask and dma_max_mapping_size > is far from obvious. The documentation doesn't exist. > Do we really have to teach all users about this hack? > Why not just make dma_max_mapping_size DTRT? Because we should not call into dma API functions for devices that are not DMA capable. 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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 DDDB3C7618B for ; Tue, 23 Jul 2019 15:38:43 +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 BD5CA223BA for ; Tue, 23 Jul 2019 15:38:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BD5CA223BA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de 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 17DC0CC4; Tue, 23 Jul 2019 15:38:34 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id BB1F1CBC; Tue, 23 Jul 2019 15:38:32 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 539BB709; Tue, 23 Jul 2019 15:38:32 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id EBAB168B02; Tue, 23 Jul 2019 17:38:30 +0200 (CEST) Date: Tue, 23 Jul 2019 17:38:30 +0200 From: Christoph Hellwig To: "Michael S. Tsirkin" Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call Message-ID: <20190723153830.GD720@lst.de> References: <20190722145509.1284-1-eric.auger@redhat.com> <20190722145509.1284-3-eric.auger@redhat.com> <20190722112704-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190722112704-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: jasowang@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, eric.auger.pro@gmail.com, robin.murphy@arm.com, hch@lst.de 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 On Mon, Jul 22, 2019 at 11:33:35AM -0400, Michael S. Tsirkin wrote: > On Mon, Jul 22, 2019 at 04:55:09PM +0200, Eric Auger wrote: > > Do not call dma_max_mapping_size for devices that have no DMA > > mask set, otherwise we can hit a NULL pointer dereference. > > > > This occurs when a virtio-blk-pci device is protected with > > a virtual IOMMU. > > > > Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()") > > Signed-off-by: Eric Auger > > Suggested-by: Christoph Hellwig > > Christoph, I wonder why did you suggest this? > The connection between dma_mask and dma_max_mapping_size > is far from obvious. The documentation doesn't exist. > Do we really have to teach all users about this hack? > Why not just make dma_max_mapping_size DTRT? Because we should not call into dma API functions for devices that are not DMA capable. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu