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virtio_input: fix DMA alignment for evts

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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_group_begin()/end() annotations to ensure evts is
isolated in its own cachelines.

Message-ID: <cd328233198a76618809bb5cd9a6ddcaa603a8a1.1767601130.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin
2025-12-29 18:24:36 -05:00
parent db191ba0c8
commit 95c7b0ad6c
1 changed files with 3 additions and 0 deletions
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3
drivers/virtio/virtio_input.c
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@@ -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_group_begin();
struct virtio_input_event evts[64];
__dma_from_device_group_end();
spinlock_t lock;
bool ready;
};