[PATCH net-next v6 00/15] ibmveth: Add multi-queue RX support

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); standard per-queue
packets/bytes/drops via netdev_stat_ops (ethtool -S keeps only
driver-specific counters; ndo_get_stats64 is the aggregate, including
retired-queue history); 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); traffic can land on any active queue. The
driver needs per-queue pools, IRQs, and NAPI to match. Legacy firmware
keeps the original hcall path.

Series layout (15 patches):

  1-2   Hypercall wrappers; MQ adapter layout (MAX_RX_QUEUES stays 1)
  3-9   Queue-aware helpers (still SQ runtime): RX, per-queue pools,
        IRQ, TX, PHYP, buffer submit (open/close 3-8); poll harden (9)
  10    Enable MQ datapath at probe/open (subordinate register helpers
        land here with first use)
  11-13 Per-queue RX/TX stats; get_channels MQ counts; debugfs buffer_pools
  14    Incremental RX resize; live ethtool -L rx
  15    Down-path rollback and mq_fallback max_rx cap

- Helper patches (3-8) reshape ibmveth_open()/close() into
  queue-aware helpers. Patch 9 hardens the SQ poll path with the same
  queue-index helpers; it does not change open/close. MQ stays off
  through 3-9: num_rx_queues stays 1 and multi_queue is false until
  patch 10. The live single-queue path still changes where the review
  required it (open/close unwind, IRQ remask, replenish lock, poll
  harden).
- Patch 10 is the switch: probe sets multi_queue from firmware, raises
  num_rx_queues, registers subordinates, and replenishes every active
  queue.
- Patch 11 moves counters per-queue and exports packets/bytes/drops
  through netdev_stat_ops. The thirteen existing -S keys stay; no
  hcall_* or pool%d_ keys.

Testing:

ppc64le PowerVM LPAR, MQ-capable firmware:
* ethtool -L cycling (16/1/8/11/1/3/16/8/1) with ping - no hangs
* ethtool -L under iperf3; link down/up during traffic
* ifdown/ifup under iperf3 RX+TX (MQ and ethtool -L rx 1)
* Legacy firmware (no MQ bit): open/close/stress on helper path
* W=1 clean at every commit (15/15 PASS, 0 warnings per-patch and
  in aggregate, ARCH=powerpc ibmveth.o)

Changes in v6:

Same 15 patches as v5. Jakub v5 review folded in; per-patch detail is
below --- on each commit.

* Both new registration wrappers use plpar_hcall(), not plpar_hcall9().
* Poll: IPv4 check through skb->data; budget 0 does not complete NAPI.
* Scale-down: publish the surviving count, then synchronize_net(),
  then destroy. num_rx_queues uses smp_store_release / smp_load_acquire.
* packets/bytes/drops through netdev_stat_ops, not private -S strings.
  Thirteen existing -S keys kept. No hcall_* or pool%d_ keys.
  replenish_* are per-queue u64; no atomics. get_base_stats() is the
  retired-queue remainder.
* Reset worker gated on NETREG_REGISTERED (cannot reopen after
  unregister).
* get_channels() keeps the live rx_count; mq_fallback caps max_rx so
  a TX-only ethtool -L is not a silent RX shrink.
* Open-fail double-free (d43732ce021f) rides in patches 3 and 6;
  standalone fix to net follows this series.

Known limitations (not this series):

* h_free_logical_lan[_queue] still log-and-continue on non-busy
  failure; fixing requires status propagation through all teardown
  callers. Pre-existing; incremental shrink copies the same path.
* Internal close+open restarts (pool_store, change_mtu) do not call
  netpoll_poll_disable(); pre-existing single-queue behaviour,
  unchanged by this series.
* CMO desired is not recomputed when a down-path set_channels publish
  is never realised (mq_fallback or failed reopen); fixing requires
  recomputing on every path that changes the realised queue count.
* Pool kobject .release is NULL; put then free_netdev() is unsafe
  under CONFIG_DEBUG_KOBJECT_RELEASE. Requires a proper release
  callback; pre-existing pattern.
* ethtool -L TX shrink uses netif_tx_stop_all_queues(), not
  netif_tx_disable(); close() already uses disable. Pre-existing;
  needs its own patch with a Fixes: tag.
* get_desired_dma() TX term is one LTB regardless of TX queue count;
  should scale with real_num_tx_queues. Pre-existing.
* max_tx from num_online_cpus() can fall below a configured tx_count
  after CPU hotplug; pre-existing.

Changes in v5:

* Restack mailed v4 (14 patches) to v5 (15):

    v4 1-8  helpers                -> v5 1-8
    (new)   SQ poll harden         -> v5 9   (before MQ enable)
    v4 9    MQ enable              -> v5 10
    v4 10   stats                  -> v5 11
    (new)   get_channels           -> v5 12  (peeled from stats)
    v4 11   debugfs                -> v5 13
    v4 12   resize                 -> v5 14
    v4 13   set_channels           -> v5 15
    v4 14   trailing poll/shutdown -> folded into v5 5/9/10/14
            (mailed "P14" was that trailer, not v5 14)
* Teardown-first resize after aggressive ethtool -L; thin defensive
  poll skip remains; no correlator generation field this series
* opened / rx_irq_setup; set_channels keys on opened (not IFF_UP)
* filter_list_dma=0 on map error; restore default-active 64 KiB pool;
  unwind pools by allocation presence; probe_cleanup clears vio
  drvdata; remove: unregister then cancel_work
* TX quiesce before freeing bounce buffers; guard start_xmit if LTB gone
* MQ H_FUNCTION recovery (reset + SQ fallback); no printk under
  replenish_lock; lock harvest with replenish; resume kicks all queues
* Per-queue update_rx_no_buffer; publish-before-free on resize;
  CMO refresh; IRQ helpers return errno
* Harvest abort (no fake GRO / UAF); poll refuses PHYP re-arm on close;
  wrap-safe skb_put; atomic set_channels; monotonic stats across shrink
* Keep mask -> sync -> napi_disable on teardown; open stays
  request_irq -> napi_enable while PHYP masked; scale-up/recovery keep
  napi_enable before enable_irq
* Pool geometry kept on free; restart_rx_queue after open/scale-down;
  remask after napi_disable; schedule_rx_queue masks only when
  napi_schedule_prep succeeds (STOP + poll no-rearm for storms)

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
* Bisect-friendly restack (helpers with first use)

Changes in v3:

* Dropped RFC; addressed style / DMA feedback from earlier revisions
* Early MQ enablement iterations (see lore links below)

Comments welcome.

---
v5 lore:
  https://lore.kernel.org/r/20260814073642.24630-1-mmc@linux.ibm.com (local)
v5 review (Jakub Kicinski):
  https://lore.kernel.org/r/20260818014710.3853684-1-kuba@kernel.org (local)
Sashiko Gemini (sashiko.dev):
  https://sashiko.dev/#/patchset/20260814073642.24630-1-mmc@linux.ibm.com
Sashiko NIPA (netdev-ai):
  https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260814073642.24630-1-mmc@linux.ibm.com

Previous versions
v5: https://lore.kernel.org/r/20260814073642.24630-1-mmc@linux.ibm.com (local)
v4: https://lore.kernel.org/r/cover.1785457143.git.mmc@linux.ibm.com (local)
v3: https://lore.kernel.org/r/20260706193603.8039-1-mmc@linux.ibm.com (local)
v2: https://lore.kernel.org/r/20260701222327.61325-1-mmc@linux.ibm.com (local)
v1: https://lore.kernel.org/r/cover.1782758799.git.mmc@linux.ibm.com (local)
v4 review (Jakub Kicinski):
  https://lore.kernel.org/r/20260806183614.3171785-1-kuba@kernel.org (local)
v3 review (Simon Horman):
  https://lore.kernel.org/r/20260714124327.GJ1364329@horms.kernel.org (local)

Mingming Cao (15):
  ibmveth: Add MQ RX hypercall wrappers and call definitions
  ibmveth: Prepare MQ RX adapter data structures
  ibmveth: Refactor RX resource allocation for MQ RX bring-up
  ibmveth: Refactor buffer pool management for per-queue MQ RX
  ibmveth: Refactor RX interrupt control for MQ RX queues
  ibmveth: Refactor TX resource allocation in open/close paths
  ibmveth: Add RX queue register helpers for MQ
  ibmveth: Add queue-aware RX buffer submit helper for MQ
  ibmveth: Harden RX poll path with helpers
  ibmveth: Enable multi-queue RX receive path
  ibmveth: Add per-queue RX and TX statistics collection
  ibmveth: Report MQ-aware RX counts in ethtool get_channels
  ibmveth: Expose per-queue buffer pool details via debugfs
  ibmveth: Implement incremental MQ RX queue resize
  ibmveth: Complete set_channels down-path and mq_fallback max_rx cap

 arch/powerpc/include/asm/hvcall.h  |    6 +-
 drivers/net/ethernet/ibm/ibmveth.c | 4159 +++++++++++++++++++++++-----
 drivers/net/ethernet/ibm/ibmveth.h |  227 +-
 3 files changed, 3630 insertions(+), 762 deletions(-)

base-commit: 1b78070aaef63512688aebfbc82365ef9d6660f1
-- 
2.50.1 (Apple Git-155)