Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754695Ab3CRWPD (ORCPT ); Mon, 18 Mar 2013 18:15:03 -0400 Received: from mga11.intel.com ([192.55.52.93]:17016 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752532Ab3CRWOu (ORCPT ); Mon, 18 Mar 2013 18:14:50 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,867,1355126400"; d="scan'208";a="308399771" Subject: [PATCH 2/2] dma-debug: Update DMA debug API to better handle multiple mappings of a buffer To: linux-kernel@vger.kernel.org From: Alexander Duyck Cc: konrad.wilk@oracle.com, joerg.roedel@amd.com, konrad@kernel.org, christoph.paasch@uclouvain.be, mingo@redhat.com, shuahkhan@gmail.com, hpa@zytor.com, akpm@linux-foundation.org, shuah.khan@hp.com, netdev@vger.kernel.org, jeffrey.t.kirsher@intel.com Date: Mon, 18 Mar 2013 15:12:49 -0700 Message-ID: <20130318221249.7349.85892.stgit@ahduyck-cp1.jf.intel.com> In-Reply-To: <20130318220241.7349.5030.stgit@ahduyck-cp1.jf.intel.com> References: <20130318220241.7349.5030.stgit@ahduyck-cp1.jf.intel.com> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2829 Lines: 69 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 --- lib/dma-debug.c | 24 +++++++++++++++++++----- 1 files changed, 19 insertions(+), 5 deletions(-) diff --git a/lib/dma-debug.c b/lib/dma-debug.c index 724bd4d..aa465d9 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -1082,13 +1082,27 @@ void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr) ref.dev = dev; ref.dev_addr = dma_addr; bucket = get_hash_bucket(&ref, &flags); - entry = bucket_find_exact(bucket, &ref); - if (!entry) - goto out; + list_for_each_entry(entry, &bucket->list, list) { + if (!exact_match(&ref, entry)) + continue; + + /* + * The same physical address can be mapped multiple + * times. Without a hardware IOMMU this results in the + * same device addresses being put into the dma-debug + * hash multiple times too. This can result in false + * positives being reported. Therefore we implement a + * best-fit algorithm here which updates the first entry + * from the hash which fits the reference value and is + * not currently listed as being checked. + */ + if (entry->map_err_type == MAP_ERR_NOT_CHECKED) { + entry->map_err_type = MAP_ERR_CHECKED; + break; + } + } - entry->map_err_type = MAP_ERR_CHECKED; -out: put_hash_bucket(bucket, &flags); } EXPORT_SYMBOL(debug_dma_mapping_error); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/