Re: [PATCH v4 net 0/6] xsk: fix AF_XDP multi-buffer Tx descriptor reclaim

[Stanislav Fomichev <sdf.kernel@gmail.com>]

On 07/19, Maciej Fijalkowski wrote:
> v3:
> https://lore.kernel.org/netdev/20260714140722.111645-1-maciej.fijalkowski@intel.com/T/
> v3->v4:
> 
> * Return standalone invalid Tx descriptors through the completion ring in
>   both the generic and zero-copy Tx paths. Advancing the Tx-ring consumer
>   releases only the ring slot; returning the descriptor address through
>   the CQ also transfers ownership of the corresponding UMEM frame back to
>   userspace.
> 
> * Remove xsk_tx_batch::consumed_descs. With standalone invalid descriptors
>   now reclaimed through the CQ, every descriptor permanently removed from
>   the Tx ring is represented by either tx_descs or reclaim_descs. Use
>   their sum for Tx-consumer advancement, shared-UMEM fairness accounting,
>   and progress detection.
> 
> * Ensure that generic reclaim-only processing publishes the updated
>   Tx-ring consumer even when no packet was submitted to the networking
>   stack.
> 
> * Update the XSK selftests to count every descriptor submitted to the Tx
>   ring as an expected CQ entry, while continuing to count only valid
>   packets as expected Rx traffic. This covers standalone invalid
>   descriptors, invalid multi-buffer packets, oversized packets, and the
>   non-verbatim STAT_TX_INVALID tests.
> 
> * Update the AF_XDP documentation to describe the completion ring as an
>   ownership-transfer mechanism and document that standalone, invalid
>   multi-buffer, and oversized Tx packets are reclaimed through the CQ.
> 
> * Add Jason's tags

Acked-by: Stanislav Fomichev <sdf@fomichev.me>

Kudos for updating the doc with the new expectations! (and I still hope
that we can separately redo the generic tx path)