[PATCH 6.18.y 1/2] dma-mapping: add __dma_from_device_group_begin()/end()

[Sasha Levin <sashal@kernel.org>]

From: "Michael S. Tsirkin" <mst@redhat.com>

[ Upstream commit ca085faabb42c31ee204235facc5a430cb9e78a9 ]

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>
Stable-dep-of: 3023c050af36 ("hwmon: (powerz) Avoid cacheline sharing for DMA buffer")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/dma-mapping.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 3e63046b899bc..f46a0848cb247 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -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
@@ -710,6 +711,18 @@ 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)
 {
-- 
2.53.0