From: Leon Romanovsky <[email protected]> Rename the DMA_ATTR_CPU_CACHE_CLEAN attribute to better reflect that it is debugging aid to inform DMA core code that CPU cache line overlaps are allowed, and refine the documentation describing its use.
Signed-off-by: Leon Romanovsky <[email protected]> --- Documentation/core-api/dma-attributes.rst | 22 ++++++++++++++-------- drivers/virtio/virtio_ring.c | 10 +++++----- include/linux/dma-mapping.h | 8 ++++---- include/trace/events/dma.h | 2 +- kernel/dma/debug.c | 2 +- 5 files changed, 25 insertions(+), 19 deletions(-) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 1d7bfad73b1c7..48cfe86cc06d7 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -149,11 +149,17 @@ For architectures that require cache flushing for DMA coherence DMA_ATTR_MMIO will not perform any cache flushing. The address provided must never be mapped cacheable into the CPU. -DMA_ATTR_CPU_CACHE_CLEAN ------------------------- - -This attribute indicates the CPU will not dirty any cacheline overlapping this -DMA_FROM_DEVICE/DMA_BIDIRECTIONAL buffer while it is mapped. This allows -multiple small buffers to safely share a cacheline without risk of data -corruption, suppressing DMA debug warnings about overlapping mappings. -All mappings sharing a cacheline should have this attribute. +DMA_ATTR_DEBUGGING_IGNORE_CACHELINES +------------------------------------ + +This attribute indicates that CPU cache lines may overlap for buffers mapped +with DMA_FROM_DEVICE or DMA_BIDIRECTIONAL. + +Such overlap may occur when callers map multiple small buffers that reside +within the same cache line. In this case, callers must guarantee that the CPU +will not dirty these cache lines after the mappings are established. When this +condition is met, multiple buffers can safely share a cache line without risking +data corruption. + +All mappings that share a cache line must set this attribute to suppress DMA +debug warnings about overlapping mappings. diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 335692d41617a..fbca7ce1c6bf0 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -2912,10 +2912,10 @@ EXPORT_SYMBOL_GPL(virtqueue_add_inbuf); * @data: the token identifying the buffer. * @gfp: how to do memory allocations (if necessary). * - * Same as virtqueue_add_inbuf but passes DMA_ATTR_CPU_CACHE_CLEAN to indicate - * that the CPU will not dirty any cacheline overlapping this buffer while it - * is available, and to suppress overlapping cacheline warnings in DMA debug - * builds. + * Same as virtqueue_add_inbuf but passes DMA_ATTR_DEBUGGING_IGNORE_CACHELINES + * to indicate that the CPU will not dirty any cacheline overlapping this buffer + * while it is available, and to suppress overlapping cacheline warnings in DMA + * debug builds. * * Caller must ensure we don't call this with other virtqueue operations * at the same time (except where noted). @@ -2928,7 +2928,7 @@ int virtqueue_add_inbuf_cache_clean(struct virtqueue *vq, gfp_t gfp) { return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, false, gfp, - DMA_ATTR_CPU_CACHE_CLEAN); + DMA_ATTR_DEBUGGING_IGNORE_CACHELINES); } EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_cache_clean); diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 29973baa05816..da44394b3a1a7 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -80,11 +80,11 @@ #define DMA_ATTR_MMIO (1UL << 10) /* - * DMA_ATTR_CPU_CACHE_CLEAN: Indicates the CPU will not dirty any cacheline - * overlapping this buffer while it is mapped for DMA. All mappings sharing - * a cacheline must have this attribute for this to be considered safe. + * DMA_ATTR_DEBUGGING_IGNORE_CACHELINES: Indicates the CPU cache line can be + * overlapped. All mappings sharing a cacheline must have this attribute for + * this to be considered safe. */ -#define DMA_ATTR_CPU_CACHE_CLEAN (1UL << 11) +#define DMA_ATTR_DEBUGGING_IGNORE_CACHELINES (1UL << 11) /* * A dma_addr_t can hold any valid DMA or bus address for the platform. It can diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h index 69cb3805ee81c..8c64bc0721fe4 100644 --- a/include/trace/events/dma.h +++ b/include/trace/events/dma.h @@ -33,7 +33,7 @@ TRACE_DEFINE_ENUM(DMA_NONE); { DMA_ATTR_NO_WARN, "NO_WARN" }, \ { DMA_ATTR_PRIVILEGED, "PRIVILEGED" }, \ { DMA_ATTR_MMIO, "MMIO" }, \ - { DMA_ATTR_CPU_CACHE_CLEAN, "CACHE_CLEAN" }) + { DMA_ATTR_DEBUGGING_IGNORE_CACHELINES, "CACHELINES_OVERLAP" }) 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 be207be749968..83e1cfe05f08d 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -601,7 +601,7 @@ 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_CPU_CACHE_CLEAN); + entry->is_cache_clean = attrs & DMA_ATTR_DEBUGGING_IGNORE_CACHELINES; bucket = get_hash_bucket(entry, &flags); hash_bucket_add(bucket, entry); -- 2.53.0
