[PATCH net-next 5/5] selftests: rss_drv: Add RSS indirection table resize tests

["Björn Töpel" <bjorn@kernel.org>]

Add resize tests to rss_drv.py. Devices without dynamic table
sizing are skipped via _require_dynamic_indir_size().

resize_periodic: set a periodic table (equal 2), shrink
channels to fold, grow back to unfold. Check the pattern is
preserved. Has main and non-default context variants.

resize_nonperiodic_reject: set a non-periodic table (equal N),
verify that channel reduction is rejected.

Pass queue_count=8 to NetDrvEnv so netdevsim is created with
enough queues for the resize tests.

Signed-off-by: Björn Töpel <bjorn@kernel.org>
---
 .../selftests/drivers/net/hw/rss_drv.py       | 101 +++++++++++++++++-
 1 file changed, 96 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/hw/rss_drv.py b/tools/testing/selftests/drivers/net/hw/rss_drv.py
index 2d1a33189076..8725500f2955 100755
--- a/tools/testing/selftests/drivers/net/hw/rss_drv.py
+++ b/tools/testing/selftests/drivers/net/hw/rss_drv.py
@@ -5,9 +5,9 @@
 Driver-related behavior tests for RSS.
 """
 
-from lib.py import ksft_run, ksft_exit, ksft_ge
-from lib.py import ksft_variants, KsftNamedVariant, KsftSkipEx
-from lib.py import defer, ethtool
+from lib.py import ksft_run, ksft_exit, ksft_eq, ksft_ge
+from lib.py import ksft_variants, KsftNamedVariant, KsftSkipEx, KsftFailEx
+from lib.py import defer, ethtool, CmdExitFailure
 from lib.py import EthtoolFamily, NlError
 from lib.py import NetDrvEnv
 
@@ -45,6 +45,18 @@ def _maybe_create_context(cfg, create_context):
     return ctx_id
 
 
+def _require_dynamic_indir_size(cfg, ch_max):
+    """Skip if the device does not dynamically size its indirection table."""
+    ethtool(f"-X {cfg.ifname} default")
+    ethtool(f"-L {cfg.ifname} combined 2")
+    small = len(_get_rss(cfg)['rss-indirection-table'])
+    ethtool(f"-L {cfg.ifname} combined {ch_max}")
+    large = len(_get_rss(cfg)['rss-indirection-table'])
+
+    if small == large:
+        raise KsftSkipEx("Device does not dynamically size indirection table")
+
+
 @ksft_variants([
     KsftNamedVariant("main", False),
     KsftNamedVariant("ctx", True),
@@ -76,11 +88,90 @@ def indir_size_4x(cfg, create_context):
         _test_rss_indir_size(cfg, test_max, context=ctx_id)
 
 
+@ksft_variants([
+    KsftNamedVariant("main", False),
+    KsftNamedVariant("ctx", True),
+])
+def resize_periodic(cfg, create_context):
+    """Test that a periodic indirection table survives channel changes.
+
+    Set a periodic table (equal 2), reduce channels to trigger a
+    fold, then increase to trigger an unfold. Verify the table pattern
+    is preserved and the size tracks the channel count.
+    """
+    channels = cfg.ethnl.channels_get({'header': {'dev-index': cfg.ifindex}})
+    ch_max = channels.get('combined-max', 0)
+    qcnt = channels['combined-count']
+
+    if ch_max < 4:
+        raise KsftSkipEx(f"Not enough queues for the test: max={ch_max}")
+
+    defer(ethtool, f"-L {cfg.ifname} combined {qcnt}")
+    ethtool(f"-L {cfg.ifname} combined {ch_max}")
+
+    _require_dynamic_indir_size(cfg, ch_max)
+
+    ctx_id = _maybe_create_context(cfg, create_context)
+    ctx_ref = f"context {ctx_id}" if ctx_id else ""
+
+    ethtool(f"-X {cfg.ifname} {ctx_ref} equal 2")
+    if not create_context:
+        defer(ethtool, f"-X {cfg.ifname} default")
+
+    orig_size = len(_get_rss(cfg, context=ctx_id)['rss-indirection-table'])
+
+    # Shrink — should fold
+    ethtool(f"-L {cfg.ifname} combined 2")
+    rss = _get_rss(cfg, context=ctx_id)
+    indir = rss['rss-indirection-table']
+
+    ksft_ge(orig_size, len(indir), "Table did not shrink")
+    ksft_eq(set(indir), {0, 1}, "Folded table has wrong queues")
+
+    # Grow back — should unfold
+    ethtool(f"-L {cfg.ifname} combined {ch_max}")
+    rss = _get_rss(cfg, context=ctx_id)
+    indir = rss['rss-indirection-table']
+
+    ksft_eq(len(indir), orig_size, "Table size not restored")
+    ksft_eq(set(indir), {0, 1}, "Unfolded table has wrong queues")
+
+
+def resize_nonperiodic_reject(cfg):
+    """Test that a non-periodic table blocks channel reduction.
+
+    Set equal weight across all queues so the table is not periodic
+    at any smaller size, then verify channel reduction is rejected.
+    """
+    channels = cfg.ethnl.channels_get({'header': {'dev-index': cfg.ifindex}})
+    ch_max = channels.get('combined-max', 0)
+    qcnt = channels['combined-count']
+
+    if ch_max < 4:
+        raise KsftSkipEx(f"Not enough queues for the test: max={ch_max}")
+
+    defer(ethtool, f"-L {cfg.ifname} combined {qcnt}")
+    ethtool(f"-L {cfg.ifname} combined {ch_max}")
+
+    _require_dynamic_indir_size(cfg, ch_max)
+
+    ethtool(f"-X {cfg.ifname} equal {ch_max}")
+    defer(ethtool, f"-X {cfg.ifname} default")
+
+    try:
+        ethtool(f"-L {cfg.ifname} combined 2")
+    except CmdExitFailure:
+        pass
+    else:
+        raise KsftFailEx("Channel reduction should fail with non-periodic table")
+
+
 def main() -> None:
     """ Ksft boiler plate main """
-    with NetDrvEnv(__file__) as cfg:
+    with NetDrvEnv(__file__, queue_count=8) as cfg:
         cfg.ethnl = EthtoolFamily()
-        ksft_run([indir_size_4x], args=(cfg, ))
+        ksft_run([indir_size_4x, resize_periodic,
+                  resize_nonperiodic_reject], args=(cfg, ))
     ksft_exit()
 
 
-- 
2.53.0