virtio_input: fix DMA cacheline alignment for evts

On non-cache-coherent platforms, when a structure contains a buffer used for DMA alongside fields that the CPU writes to, cacheline sharing can cause data corruption.

The evts array is used for DMA_FROM_DEVICE operations via virtqueue_add_inbuf(). The adjacent lock and ready fields are written by the CPU during normal operation. If these share cachelines with evts, CPU writes can corrupt DMA data.

Add __dma_from_device_aligned_begin/end annotations to ensure evts is isolated in its own cachelines.

---
 drivers/virtio/virtio_input.c | 3 +++
 1 file changed, 3 insertions(+)

index d0728285b6ce..774494754a99 100644
@@ -4,6 +4,7 @@
 #include <linux/virtio_config.h>
 #include <linux/input.h>
 #include <linux/slab.h>
+#include <linux/dma-mapping.h>
 
 #include <uapi/linux/virtio_ids.h>
 #include <uapi/linux/virtio_input.h>

@@ -16,7 +17,9 @@ struct virtio_input {
 	char                       serial[64];
 	char                       phys[64];
 	struct virtqueue           *evt, *sts;
+	__dma_from_device_aligned_begin
 	struct virtio_input_event  evts[64];
+	__dma_from_device_aligned_end
 	spinlock_t                 lock;
 	bool                       ready;
 };

MST

Add __dma_from_device_aligned_begin annotation before the data buffer in struct virtrng_info to ensure proper cacheline alignment on non-cache-coherent platforms.

The data buffer is used for DMA_FROM_DEVICE via virtqueue_add_inbuf() and is adjacent to CPU-written fields (data_avail, data_idx). Without proper alignment, the device writing to the DMA buffer and the CPU writing to adjacent fields could corrupt each other's data on platforms where DMA cache maintenance is at cacheline granularity.

---
 drivers/char/hw_random/virtio-rng.c | 2 ++
 1 file changed, 2 insertions(+)

index dd998f4fe4f2..fb3c57bee3b1 100644
@@ -11,6 +11,7 @@
 #include <linux/spinlock.h>
 #include <linux/virtio.h>
 #include <linux/virtio_rng.h>
+#include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 

@@ -28,6 +29,7 @@ struct virtrng_info {
 	unsigned int data_avail;
 	unsigned int data_idx;
 	/* minimal size returned by rng_buffer_size() */
+	__dma_from_device_aligned_begin
 #if SMP_CACHE_BYTES < 32
 	u8 data[32];
 #else

MST