On Mon, Nov 6, 2023 at 4:03 PM Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> wrote: > > On Mon, Nov 6, 2023 at 3:55 PM David Ahern <dsahern@xxxxxxxxxx> wrote: > > > > On 11/6/23 4:32 PM, Stanislav Fomichev wrote: > > >> The concise notification API returns tokens as a range for > > >> compression, encoding as two 32-bit unsigned integers start + length. > > >> It allows for even further batching by returning multiple such ranges > > >> in a single call. > > > > > > Tangential: should tokens be u64? Otherwise we can't have more than > > > 4gb unacknowledged. Or that's a reasonable constraint? > > > > > > > Was thinking the same and with bits reserved for a dmabuf id to allow > > multiple dmabufs in a single rx queue (future extension, but build the > > capability in now). e.g., something like a 37b offset (128GB dmabuf > > size), 19b length (large GRO), 8b dmabuf id (lots of dmabufs to a queue). > > Agreed. Converting to 64b now sounds like a good forward looking revision. The concept of IDing a dma-buf came up in a couple of different contexts. First, in the context of us giving the dma-buf ID to the user on recvmsg() to tell the user the data is in this specific dma-buf. The second context is here, to bind dma-bufs with multiple user-visible IDs to an rx queue. My issue here is that I don't see anything in the struct dma_buf that can practically serve as an ID: https://elixir.bootlin.com/linux/v6.6-rc7/source/include/linux/dma-buf.h#L302 Actually, from the userspace, only the name of the dma-buf seems queryable. That's only unique if the user sets it as such. The dmabuf FD can't serve as an ID. For our use case we need to support 1 process doing the dma-buf bind via netlink, sharing the dma-buf FD to another process, and that process receives the data. In this case the FDs shown by the 2 processes may be different. Converting to 64b is a trivial change I can make now, but I'm not sure how to ID these dma-bufs. Suggestions welcome. I'm not sure the dma-buf guys will allow adding a new ID + APIs to query said dma-buf ID. -- Thanks, Mina
