On Thu, Jan 08, 2026 at 09:07:53AM -0500, Michael S. Tsirkin wrote:
On Thu, Jan 08, 2026 at 03:04:07PM +0100, Stefano Garzarella wrote:
On Mon, Jan 05, 2026 at 03:23:17AM -0500, Michael S. Tsirkin wrote:
> 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.
>
> Signed-off-by: Michael S. Tsirkin <[email protected]>
> ---
> net/vmw_vsock/virtio_transport.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/vmw_vsock/virtio_transport.c
b/net/vmw_vsock/virtio_transport.c
> index 8c867023a2e5..bb94baadfd8b 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -17,6 +17,7 @@
> #include <linux/virtio_ids.h>
> #include <linux/virtio_config.h>
> #include <linux/virtio_vsock.h>
> +#include <linux/dma-mapping.h>
> #include <net/sock.h>
> #include <linux/mutex.h>
> #include <net/af_vsock.h>
> @@ -59,8 +60,9 @@ struct virtio_vsock {
> */
> struct mutex event_lock;
> bool event_run;
> + __dma_from_device_group_begin();
> struct virtio_vsock_event event_list[8];
> -
> + __dma_from_device_group_end();
Can we keep the blank line before `guest_cid` so that the comment before
this section makes sense? (regarding the lock required to access these
fields)
Thanks,
Stefano
A follow up patch re-introduces it, so I don't think it matters?
Yes, I saw it later. Of course I don't want you to resend the whole
series just for this. So if you have to resend the series for other
reasons, I would avoid removing the line here because I don't see any
value on removing it and add back later.
In both cases:
Acked-by: Stefano Garzarella <[email protected]>
> u32 guest_cid;
> bool seqpacket_allow;
>
> --
> MST
>
