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Sun, 09 Dec 2018 17:15:15 -0800 (PST) From: Nicolas Boichat To: Will Deacon Subject: [PATCH v6 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables Date: Mon, 10 Dec 2018 09:15:01 +0800 Message-Id: <20181210011504.122604-1-drinkcat@chromium.org> X-Mailer: git-send-email 2.20.0.rc2.403.gdbc3b29805-goog MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181209_171527_854569_42F581E3 X-CRM114-Status: GOOD ( 14.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , Levin Alexander , linux-mm@kvack.org, Christoph Lameter , Huaisheng Ye , Joerg Roedel , Matthew Wilcox , hch@infradead.org, linux-arm-kernel@lists.infradead.org, David Rientjes , yingjoe.chen@mediatek.com, Vlastimil Babka , Tomasz Figa , Mike Rapoport , hsinyi@chromium.org, Matthias Brugger , Joonsoo Kim , Yong Wu , Robin Murphy , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Pekka Enberg , iommu@lists.linux-foundation.org, Andrew Morton , Mel Gorman Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org This is a follow-up to the discussion in [1], [2]. IOMMUs using ARMv7 short-descriptor format require page tables (level 1 and 2) to be allocated within the first 4GB of RAM, even on 64-bit systems. For L1 tables that are bigger than a page, we can just use __get_free_pages with GFP_DMA32 (on arm64 systems only, arm would still use GFP_DMA). For L2 tables that only take 1KB, it would be a waste to allocate a full page, so we considered 3 approaches: 1. This series, adding support for GFP_DMA32 slab caches. 2. genalloc, which requires pre-allocating the maximum number of L2 page tables (4096, so 4MB of memory). 3. page_frag, which is not very memory-efficient as it is unable to reuse freed fragments until the whole page is freed. [3] This series is the most memory-efficient approach. stable@ note: We confirmed that this is a regression, and IOMMU errors happen on 4.19 and linux-next/master on MT8173 (elm, Acer Chromebook R13). The issue most likely starts from commit ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32"), i.e. 4.15, and presumably breaks a number of Mediatek platforms (and maybe others?). [1] https://lists.linuxfoundation.org/pipermail/iommu/2018-November/030876.html [2] https://lists.linuxfoundation.org/pipermail/iommu/2018-December/031696.html [3] https://patchwork.codeaurora.org/patch/671639/ Changes since v1: - Add support for SLAB_CACHE_DMA32 in slab and slub (patches 1/2) - iommu/io-pgtable-arm-v7s (patch 3): - Changed approach to use SLAB_CACHE_DMA32 added by the previous commit. - Use DMA or DMA32 depending on the architecture (DMA for arm, DMA32 for arm64). Changes since v2: - Reworded and expanded commit messages - Added cache_dma32 documentation in PATCH 2/3. v3 used the page_frag approach, see [3]. Changes since v4: - Dropped change that removed GFP_DMA32 from GFP_SLAB_BUG_MASK: instead we can just call kmem_cache_*alloc without GFP_DMA32 parameter. This also means that we can drop PATCH v4 1/3, as we do not make any changes in GFP flag verification. - Dropped hunks that added cache_dma32 sysfs file, and moved the hunks to PATCH v5 3/3, so that maintainer can decide whether to pick the change independently. Changes since v5: - Rename ARM_V7S_TABLE_SLAB_CACHE to ARM_V7S_TABLE_SLAB_FLAGS. - Add stable@ to cc. Nicolas Boichat (3): mm: Add support for kmem caches in DMA32 zone iommu/io-pgtable-arm-v7s: Request DMA32 memory, and improve debugging mm: Add /sys/kernel/slab/cache/cache_dma32 Documentation/ABI/testing/sysfs-kernel-slab | 9 +++++++++ drivers/iommu/io-pgtable-arm-v7s.c | 19 +++++++++++++++---- include/linux/slab.h | 2 ++ mm/slab.c | 2 ++ mm/slab.h | 3 ++- mm/slab_common.c | 2 +- mm/slub.c | 16 ++++++++++++++++ tools/vm/slabinfo.c | 7 ++++++- 8 files changed, 53 insertions(+), 7 deletions(-) -- 2.20.0.rc2.403.gdbc3b29805-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel