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Tsirkin" , Petr Tesarik , Jonathan Corbet , Shuah Khan , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , Jason Gunthorpe , Leon Romanovsky , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Joerg Roedel , Will Deacon , Andrew Morton Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux.dev, linux-rdma@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 4/8] dma-mapping: Introduce DMA require coherency attribute Date: Wed, 11 Mar 2026 21:08:47 +0200 Message-ID: <20260311-dma-debug-overlap-v2-4-e00bc2ca346d@nvidia.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260311-dma-debug-overlap-v2-0-e00bc2ca346d@nvidia.com> References: <20260311-dma-debug-overlap-v2-0-e00bc2ca346d@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.15-dev-18f8f Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 765961A000B X-Stat-Signature: 55hyx8axxrw7s3c71tgqozi3w8rueseq X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1773256149-129849 X-HE-Meta: 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 0r8WGBYg 1cYEOcZpiejXY4ZQGH1nQ86P/xTtTkzWrWktpdptydqu0TGuug2ZpAIekp/HVMG8818mi2LZBpoBYYh4bK0J4xjTRim0L1Qey6C3wcQ4ZvgPzwn93+a0+Y1nom8rse3Goxt2W9IqbpQ1hOKw0VMQgF77VJzj6+GLD8ufH5VhdxniX6q7eHaCNbu5gL5uHtqQgdrHaksvddSr7tNRxI2Bc2DAQRf1rYrnsxkWre4XgHySDczw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Leon Romanovsky The mapping buffers which carry this attribute require DMA coherent system. This means that they can't take SWIOTLB path, can perform CPU cache overlap and doesn't perform cache flushing. Signed-off-by: Leon Romanovsky --- Documentation/core-api/dma-attributes.rst | 12 ++++++++++++ include/linux/dma-mapping.h | 7 +++++++ include/trace/events/dma.h | 3 ++- kernel/dma/debug.c | 3 ++- kernel/dma/mapping.c | 6 ++++++ 5 files changed, 29 insertions(+), 2 deletions(-) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 48cfe86cc06d7..69d094f144c70 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -163,3 +163,15 @@ data corruption. All mappings that share a cache line must set this attribute to suppress DMA debug warnings about overlapping mappings. + +DMA_ATTR_REQUIRE_COHERENT +------------------------- + +The mapping buffers which carry this attribute require DMA coherent system. This means +that they can't take SWIOTLB path, can perform CPU cache overlap and doesn't perform +cache flushing. + +If the mapping has this attribute then it is prevented from running on systems +where these cache artifacts can cause corruption, and as such doesn't need +cache overlapping debugging code (same behavior as for +DMA_ATTR_DEBUGGING_IGNORE_CACHELINES). diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index da44394b3a1a7..482b919f040f7 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -86,6 +86,13 @@ */ #define DMA_ATTR_DEBUGGING_IGNORE_CACHELINES (1UL << 11) +/* + * DMA_ATTR_REQUIRE_COHERENT: Indicates that DMA coherency is required. + * All mappings that carry this attribute can't work with SWIOTLB and cache + * flushing. + */ +#define DMA_ATTR_REQUIRE_COHERENT (1UL << 12) + /* * A dma_addr_t can hold any valid DMA or bus address for the platform. It can * be given to a device to use as a DMA source or target. It is specific to a diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h index 8c64bc0721fe4..63597b0044247 100644 --- a/include/trace/events/dma.h +++ b/include/trace/events/dma.h @@ -33,7 +33,8 @@ TRACE_DEFINE_ENUM(DMA_NONE); { DMA_ATTR_NO_WARN, "NO_WARN" }, \ { DMA_ATTR_PRIVILEGED, "PRIVILEGED" }, \ { DMA_ATTR_MMIO, "MMIO" }, \ - { DMA_ATTR_DEBUGGING_IGNORE_CACHELINES, "CACHELINES_OVERLAP" }) + { DMA_ATTR_DEBUGGING_IGNORE_CACHELINES, "CACHELINES_OVERLAP" }, \ + { DMA_ATTR_REQUIRE_COHERENT, "REQUIRE_COHERENT" }) DECLARE_EVENT_CLASS(dma_map, TP_PROTO(struct device *dev, phys_addr_t phys_addr, dma_addr_t dma_addr, diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index 83e1cfe05f08d..0677918f06a80 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -601,7 +601,8 @@ static void add_dma_entry(struct dma_debug_entry *entry, unsigned long attrs) unsigned long flags; int rc; - entry->is_cache_clean = attrs & DMA_ATTR_DEBUGGING_IGNORE_CACHELINES; + entry->is_cache_clean = attrs & (DMA_ATTR_DEBUGGING_IGNORE_CACHELINES | + DMA_ATTR_REQUIRE_COHERENT); bucket = get_hash_bucket(entry, &flags); hash_bucket_add(bucket, entry); diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 3928a509c44c2..6d3dd0bd3a886 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -164,6 +164,9 @@ dma_addr_t dma_map_phys(struct device *dev, phys_addr_t phys, size_t size, if (WARN_ON_ONCE(!dev->dma_mask)) return DMA_MAPPING_ERROR; + if (!dev_is_dma_coherent(dev) && (attrs & DMA_ATTR_REQUIRE_COHERENT)) + return DMA_MAPPING_ERROR; + if (dma_map_direct(dev, ops) || (!is_mmio && arch_dma_map_phys_direct(dev, phys + size))) addr = dma_direct_map_phys(dev, phys, size, dir, attrs); @@ -235,6 +238,9 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, BUG_ON(!valid_dma_direction(dir)); + if (!dev_is_dma_coherent(dev) && (attrs & DMA_ATTR_REQUIRE_COHERENT)) + return -EOPNOTSUPP; + if (WARN_ON_ONCE(!dev->dma_mask)) return 0; -- 2.53.0