[PATCH net v4 0/2] net/mlx5e: Prevent stale XSK buffer release on refill retries

[Jerome Tollet <jtollet@cisco.com>]

Prevent duplicate XSK buffer release when a deferred RX refill fails and
the same WQE is retried.

Patch 1 fixes legacy cyclic RQ. It is unchanged from v3 and retains
Dragos' Reviewed-by tag.

Patch 2 fixes the analogous striding-RQ MPWQE path. Following Dragos'
review, it now fills skip_release_bitmap in the common error path of
mlx5e_xsk_alloc_rx_mpwqe(), consistently with mlx5e_alloc_rx_mpwqe().

Targeted fault injection covered both an early allocation failure and a
partial 8-of-16-buffer unwind. With three consecutive failures for one
MPWQE, the original 16 XSK buffers were released only once, retries saw a
full bitmap, and a later successful allocation cleared it. A clean
20-second AF_XDP zero-copy pressure run exercised 1,575,262 buffer
allocation failures without invalid descriptors, WQE errors, or kernel
warnings.

Changes in v4:
- Keep patch 1 unchanged.
- Move the MPWQE bitmap update from the release loop to the common XSK
  allocator error path, as suggested by Dragos.
- Validate both early and partial allocation failures and run an
  additional zero-copy pressure test.

v3: https://lore.kernel.org/netdev/cover.1787347981.git.jtollet@cisco.com/

Jerome Tollet (2):
  net/mlx5e: Prevent stale XSK buffer release on refill retry
  net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry

 drivers/net/ethernet/mellanox/mlx5/core/en/xsk/rx.c | 2 ++
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c     | 7 +++++--
 2 files changed, 7 insertions(+), 2 deletions(-)


base-commit: 4e15e89faac9f308baeb01f46c13a051814d2449
-- 
2.55.0