[PATCH net 0/2] ionic: fix Tx stalls on TSO skbs larger than the Tx ring

["Nikhil P. Rao" <nikhil.rao@amd.com>]

ionic uses one Tx descriptor per TSO segment but never tells the stack
how many it can hold, so tso_max_segs stays at its 65535 default. A TSO
skb with more segments than the Tx ring holds can never be posted: the
queue stops with the ring empty, nothing wakes it, and the netdev
watchdog fires again after every reset. A 64 KB TSO skb needs more
than 1023 segments, the limit of the default 1024-entry ring, once the
MSS is below 64 bytes.

Patch 1 rejects Tx ring sizes below 64. The completion path wakes a
stopped Tx queue only once 44 descriptors are free, so a smaller ring
can stall on its own, and patch 2 would otherwise let such a ring lower
gso_max_segs to a uselessly small value.

Patch 2 advertises tso_max_segs from the Tx ring size and keeps it in
step with ethtool -G, so the stack sizes TSO skbs to fit the ring and
segments larger ones in software.

Tested with the in-tree driver in a VM with the PF passed through:
GSO frames with a virtio-net header and about 1500 segments, injected
through a tap redirected to the ionic netdev with tc mirred, stalled the
Tx queue before the series and are sent without a stall after it;
tso_max_segs follows ethtool -G with the interface up and down, and a
Tx ring of 32 is rejected.

This series was developed with the help of an LLM-based coding
assistant (Claude).

---
Nikhil P. Rao (2):
      ionic: reject Tx ring sizes below the minimum
      ionic: limit TSO segments to the Tx ring size

 drivers/net/ethernet/pensando/ionic/ionic_ethtool.c | 19 ++++++++++++++++---
 drivers/net/ethernet/pensando/ionic/ionic_lif.c     | 10 +++++++---
 drivers/net/ethernet/pensando/ionic/ionic_lif.h     | 10 ++++++++++
 3 files changed, 33 insertions(+), 6 deletions(-)
---
base-commit: a36b9e205cb3c452ab96cc783e63465d466fe615
change-id: 20261107-b4-ionic-tso-max-segs-057bde9cfe49

Best regards,
--  
Nikhil P. Rao <nikhil.rao@amd.com>