[PATCH net-next v4 00/14] ibmveth: Add multi-queue RX support

[Mingming Cao <mmc@linux.ibm.com>]

Hi,

Power11 PHYP adds Virtual Ethernet multi-queue (MQ) RX: multiple
logical-LAN RX queues, per-queue buffer posting, and completion
delivery. Guest Linux did not use that; ibmveth still registered one
RX queue even when PHYP was MQ-capable.

This series adds the ibmveth MQ client for net-next. When PHYP
advertises IBMVETH_ILLAN_RX_MULTI_QUEUE_SUPPORT via H_ILLAN_ATTRIBUTES,
probe enables MQ with a default RX count of min(num_online_cpus(), 8)
(same cap as TX today); ethtool -L can raise RX up to 16. Packets are
received on per-queue NAPI. Older firmware without the bit is unchanged.
Queue selection remains firmware-defined (PHYP hash). Ethtool RSS hash
get/set for that algorithm is deferred to a follow-up series so this
one stays MQ datapath only.

User-visible bits: ethtool -l/-L (channels), ethtool -S and
ndo_get_stats64 (per-queue + aggregate), and a read-only debugfs
buffer_pools dump (v3's multi-line sysfs dump moved to debugfs; the
historical queue-0 poolN/ sysfs ABI is unchanged).

Background:

ibmveth today uses one logical LAN, one set of buffer pools, and one
NAPI context. PHYP MQ mode gives each RX queue its own handle (post via
H_ADD_LOGICAL_LAN_BUFFERS_QUEUE, subordinate register via
H_REG_LOGICAL_LAN_QUEUE). Legacy firmware keeps the original hcall path.

Series layout (14 patches):

  1-2   Hypercall wrappers; MQ adapter layout (MAX_RX_QUEUES stays 1)
  3-8   Refactor open/close into queue-aware helpers (still SQ runtime)
  9     Enable MQ datapath at probe/open (subordinate register helpers
        land here with first use; probe pool-kobj fail paths put
        already-created pool kobjects)
  10-11 Per-queue RX/TX stats; debugfs buffer_pools
  12-13 Incremental RX resize; ethtool set_channels
  14    Poll/close fixes after aggressive ethtool -L

Patch 2 is layout-only. Statistics types land with first use
(hcall_stats in 7, rx/tx qstats in 10). Patches 3-8 do not change
runtime behaviour until patch 9. v3's separate big-bang open/close
pipeline patch is gone; wiring is incremental across 3-8.

Testing:

ppc64le PowerVM LPAR, MQ-capable firmware:
* ethtool -L cycling (16/1/8/11/1/3/16/8/1) with ping
* ethtool -L under iperf3; link down/up during traffic
* ifdown/ifup under iperf3 RX+TX (SQ and MQ)
* Legacy firmware (no MQ bit): open/close/stress on helper path
* allmodconfig W=1 clean at each patch (bisect-friendly restack)

Changes in v4:

Addresses Simon's v3 review and related fixes:
* First-use helpers/includes (irqdomain.h with first dispose); no
  unused statics; dropped orphan open/close pipeline patch
* Open/close unwind (free LAN before RX pools); no double TX teardown
* MQ open: replenish all queues before PHYP unmask; H_FUNCTION on
  subordinate register is a hard open failure
* Resize/set_channels hardenings; stats probe-lifetime + sum-on-read;
  buffer_pools diagnostic on debugfs
* Patch 9: put already-created pool kobjects on probe failure paths
* Patch 14: correlator skip, skb tailroom check, napi_complete_done
  shutdown return < budget

Comments welcome.

---
Previous versions
v3: https://lore.kernel.org/r/20260706193603.8039-1-mmc@linux.ibm.com
v2: https://lore.kernel.org/r/20260701222327.61325-1-mmc@linux.ibm.com
v1: https://lore.kernel.org/r/cover.1782758799.git.mmc@linux.ibm.com
v3 review (Simon, from 05/15):
  https://lore.kernel.org/r/20260714124327.GJ1364329@horms.kernel.org