On Fri, May 26, 2023 at 1:47 PM Liang Chen [off-list ref] wrote:

Currently, DMA operations of virtio devices' data buffer are encapsulated
within the underlying virtqueue implementation. DMA map/unmap operations
are performed for each data buffer attached to/detached from the virtqueue,
which is transparent and invisible to the higher-level virtio device
drivers. This encapsulation makes it not viable for device drivers to
introduce certain mechanisms, such as page pool, that require explicit
management of DMA map/unmap. Therefore, by inserting a pre-handler before
the generic DMA map/unmap operations, virtio device drivers have the
opportunity to participate in DMA operations.

Signed-off-by: Liang Chen <redacted>

So Xuan is doing AF_XDP for the virtio-net that allows the DMA to be
mapped at least by the virtio-net.

It looks like a way to allow virtio-net to map and unmap the DMA
buffer by itself, but this patch goes into another way which seems to
query the address from the virtio core.

Personally, I think map and sync by the virtio-net driver seems clean.
But we can see.

Thanks