From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751883AbdIODA0 (ORCPT ); Thu, 14 Sep 2017 23:00:26 -0400 Received: from smtpbgau1.qq.com ([54.206.16.166]:55486 "EHLO smtpbgau1.qq.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751733AbdIODAZ (ORCPT ); Thu, 14 Sep 2017 23:00:25 -0400 X-QQ-mid: bizesmtp2t1505444405ts7epzsan X-QQ-SSF: 01100000008000F0FNF0B00A0000000 X-QQ-FEAT: s7pJguWOSDBh5hW5TXhNx4nGxCWdhb5w1Tgw/1nHPrCy13+RPb9lu+QJk2KKG zWBKnRJ8qQWhqrd2GWmuZpgmXQzaKFrHFqCrFHfoCNyoOewFTUPYw5iFTvx5FgvpO+DRzgm 5jc8KjehIJBertN67AlJV75XiQyTQqxKijiuNWcFngTzPXwDPsu6DLOtjDniSbep8RkE+6c PkJRBVhHH4CH8fT7Hr78JubTPyYHoWC3/bkmUXP6BJreY4ncDBKyRXVZJm7OT6EzUwTtWoE 6RoO93Fw/dTX4kb0bUw5Xv+8H7vocr9ied1qTzeUdccicB X-QQ-GoodBg: 0 From: Huacai Chen To: Andrew Morton Cc: Fuxin Zhang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huacai Chen , stable@vger.kernel.org Subject: [PATCH V4 2/3] mm: dmapool: Align to ARCH_DMA_MINALIGN in non-coherent DMA mode Date: Fri, 15 Sep 2017 11:00:54 +0800 Message-Id: <1505444454-21321-1-git-send-email-chenhc@lemote.com> X-Mailer: git-send-email 2.7.0 X-QQ-SENDSIZE: 520 Feedback-ID: bizesmtp:lemote.com:qybgforeign:qybgforeign2 X-QQ-Bgrelay: 1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In non-coherent DMA mode, kernel uses cache flushing operations to maintain I/O coherency, so the dmapool objects should be aligned to ARCH_DMA_MINALIGN. Otherwise, it will cause data corruption, at least on MIPS: Step 1, dma_map_single Step 2, cache_invalidate (no writeback) Step 3, dma_from_device Step 4, dma_unmap_single If a DMA buffer and a kernel structure share a same cache line, and if the kernel structure has dirty data, cache_invalidate (no writeback) will cause data lost. Cc: stable@vger.kernel.org Signed-off-by: Huacai Chen --- mm/dmapool.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/dmapool.c b/mm/dmapool.c index 4d90a64..2ac6f4a 100644 --- a/mm/dmapool.c +++ b/mm/dmapool.c @@ -140,6 +140,9 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, else if (align & (align - 1)) return NULL; + if (!plat_device_is_coherent(dev)) + align = max_t(size_t, align, dma_get_cache_alignment()); + if (size == 0) return NULL; else if (size < 4) -- 2.7.0