tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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vsock/virtio: fix DMA alignment for event_list

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 event_list array is used for DMA_FROM_DEVICE operations via
virtqueue_add_inbuf(). The adjacent event_run and guest_cid fields are
written by the CPU while the buffer is available, so mapped for the
device. If these share cachelines with event_list, CPU writes can
corrupt DMA data.

Add __dma_from_device_group_begin()/end() annotations to ensure event_list
is isolated in its own cachelines.

Message-ID: <f19ebd74f70c91cab4b0178df78cf6a6e107a96b.1767601130.git.mst@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Michael S. Tsirkin 63dfad05 5fc6dd15

+3
+3
net/vmw_vsock/virtio_transport.c
··· 17 17 #include <linux/virtio_ids.h> 18 18 #include <linux/virtio_config.h> 19 19 #include <linux/virtio_vsock.h> 20 + #include <linux/dma-mapping.h> 20 21 #include <net/sock.h> 21 22 #include <linux/mutex.h> 22 23 #include <net/af_vsock.h> ··· 60 59 */ 61 60 struct mutex event_lock; 62 61 bool event_run; 62 + __dma_from_device_group_begin(); 63 63 struct virtio_vsock_event event_list[8]; 64 + __dma_from_device_group_end(); 64 65 65 66 u32 guest_cid; 66 67 bool seqpacket_allow;