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dma-mapping: add __dma_from_device_group_begin()/end() 

When a structure contains a buffer that DMA writes to alongside fields
that the CPU writes to, cache line sharing between the DMA buffer and
CPU-written fields can cause data corruption on non-cache-coherent
platforms.

Add __dma_from_device_group_begin()/end() annotations to ensure proper
alignment to prevent this:

struct my_device {
	spinlock_t lock1;
	__dma_from_device_group_begin();
	char dma_buffer1[16];
	char dma_buffer2[16];
	__dma_from_device_group_end();
	spinlock_t lock2;
};

Message-ID: <19163086d5e4704c316f18f6da06bc1c72968904.1767601130.git.mst@redhat.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2025-12-29 03:53:39 -05:00
parent f6a15d8549
commit ca085faabb
1 changed files with 13 additions and 0 deletions
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13
include/linux/dma-mapping.h
View File

@ -7,6 +7,7 @@
#include <linux/dma-direction.h>
#include <linux/scatterlist.h>
#include <linux/bug.h>
#include <linux/cache.h>
/**
* List of possible attributes associated with a DMA mapping. The semantics
@ -703,6 +704,18 @@ static inline int dma_get_cache_alignment(void)
}
#endif
#ifdef ARCH_HAS_DMA_MINALIGN
#define ____dma_from_device_aligned __aligned(ARCH_DMA_MINALIGN)
#else
#define ____dma_from_device_aligned
#endif
/* Mark start of DMA buffer */
#define __dma_from_device_group_begin(GROUP) \
__cacheline_group_begin(GROUP) ____dma_from_device_aligned
/* Mark end of DMA buffer */
#define __dma_from_device_group_end(GROUP) \
__cacheline_group_end(GROUP) ____dma_from_device_aligned
static inline void *dmam_alloc_coherent(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t gfp)
{