From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shuah Khan Subject: Re: [PATCH 2/2] dma-debug: Update DMA debug API to better handle multiple mappings of a buffer Date: Tue, 19 Mar 2013 14:30:22 -0600 Message-ID: <1363725022.4519.11.camel@lorien2> References: <20130318220241.7349.5030.stgit@ahduyck-cp1.jf.intel.com> <20130318221249.7349.85892.stgit@ahduyck-cp1.jf.intel.com> Reply-To: shuah.khan@hp.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, joerg.roedel@amd.com, konrad@kernel.org, christoph.paasch@uclouvain.be, mingo@redhat.com, hpa@zytor.com, akpm@linux-foundation.org, netdev@vger.kernel.org, jeffrey.t.kirsher@intel.com, shuah.khan@hp.com To: Alexander Duyck Return-path: In-Reply-To: <20130318221249.7349.85892.stgit@ahduyck-cp1.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, 2013-03-18 at 15:12 -0700, Alexander Duyck wrote: > There were reports of the igb driver unmapping buffers without calling > dma_mapping_error. On closer inspection issues were found in the DMA debug > API and how it handled multiple mappings of the same buffer. > > The issue I found is the fact that the debug_dma_mapping_error would only set > the map_err_type to MAP_ERR_CHECKED in the case that the was only one match > for device and device address. However in the case of non-IOMMU, multiple > addresses existed and as a result it was not setting this field once a > second mapping was instantiated. I have resolved this by changing the search > so that it instead will now set MAP_ERR_CHECKED on the first buffer that > matches the device and DMA address that is currently in the state > MAP_ERR_NOT_CHECKED. > > A secondary side effect of this patch is that in the case of multiple buffers > using the same address only the last mapping will have a valid map_err_type. > The previous mappings will all end up with map_err_type set to > MAP_ERR_CHECKED because of the dma_mapping_error call in debug_dma_map_page. > However this behavior may be preferable as it means you will likely only see > one real error per multi-mapped buffer, versus the current behavior of > multiple false errors mer multi-mapped buffer. > > Signed-off-by: Alexander Duyck > --- Looks good. Tested it as well. Reviewed-by: shuah.khan@hp.com Tested-by: shuah.khan@hp.com Thanks for finding and fixing the problem. -- Shuah