Merge branch 'ethtool-dynamic-rss-context-indirection-table-resizing'

Merge branch 'ethtool-dynamic-rss-context-indirection-table-resizing'

Björn Töpel says:

====================
ethtool: Dynamic RSS context indirection table resizing

Some NICs (e.g. bnxt) change their RSS indirection table size based on
the queue count, because the hardware table is a shared resource. The
ethtool core locks ctx->indir_size at context creation, so drivers
have to reject channel changes when RSS contexts exist.

This series adds resize helpers and wires them up in bnxt. It also
adds tracking of the user provided indirection table size to the
ethtool core.

Patch 1 tracks the user-provided indirection table size (user_size)
in ctx->indir_user_size for non-default RSS contexts and in
dev->ethtool->rss_indir_user_size for context 0. It is set when the
indirection table is configured via netlink or ioctl, and cleared to
zero on reset-to-default.

IFF_RXFH_CONFIGURED is removed, and replaced with rss_indir_user_size.
The flag is redundant now that user_size captures the same
information.

Patch 2 adds core resize helpers:
  ethtool_rxfh_indir_can_resize() - read-only validation for context 0
  ethtool_rxfh_indir_resize() - fold/unfold context 0 table in place
  ethtool_rxfh_ctxs_can_resize() - validate all non-default contexts
  ethtool_rxfh_ctxs_resize() - resize all non-default contexts,
    with locking and RSS_NTF notifications

Patch 3 uses the resize helpers in bnxt_set_channels().

Patch 4 adds HW tests in rss_drv.py (devices without dynamic table
sizing are skipped):
  resize_periodic - fold/unfold with a non-default [3,2,1,0]
    sub-table (user_size=4), verifying exact content preservation
    (main + ctx)
  resize_below_user_size_reject - periodic sub-table with user_size
    between big and small device table sizes; verifies that shrinking
    below user_size is rejected even when the table is periodic
    (main + ctx)
  resize_nonperiodic_reject - non-periodic table blocks channel
    reduction, with an extra periodic context to exercise
    multi-context validation (main + ctx)
  resize_nonperiodic_no_corruption - failed resize leaves table
    contents and channel count unchanged (main + ctx)

Running the tests:

  # On real hardware
  sudo NETIF=eth0 ./rss_drv.py
====================

Link: https://patch.msgid.link/20260320085826.1957255-1-bjorn@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>