selftests: drv-net: rss_ctx: check behavior of indirection table resizing

Some devices dynamically increase and decrease the size of the RSS
indirection table based on the number of enabled queues.
When that happens driver must maintain the balance of entries
(preferably duplicating the smaller table).
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20240708213627.226025-5-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/drivers/net/hw/rss_ctx.py

@@ -5,7 +5,7 @@ import datetime
 import random
 from lib.py import ksft_run, ksft_pr, ksft_exit, ksft_eq, ksft_ge, ksft_lt
 from lib.py import NetDrvEpEnv
-from lib.py import NetdevFamily
+from lib.py import EthtoolFamily, NetdevFamily
 from lib.py import KsftSkipEx
 from lib.py import rand_port
 from lib.py import ethtool, ip, defer, GenerateTraffic, CmdExitFailure
@@ -211,6 +211,39 @@ def test_rss_queue_reconfigure(cfg, main_ctx=True):
         raise Exception(f"Driver didn't prevent us from deactivating a used queue (context {ctx_id})")
 
 
+def test_rss_resize(cfg):
+    """Test resizing of the RSS table.
+
+    Some devices dynamically increase and decrease the size of the RSS
+    indirection table based on the number of enabled queues.
+    When that happens driver must maintain the balance of entries
+    (preferably duplicating the smaller table).
+    """
+
+    channels = cfg.ethnl.channels_get({'header': {'dev-index': cfg.ifindex}})
+    ch_max = channels['combined-max']
+    qcnt = channels['combined-count']
+
+    if ch_max < 2:
+        raise KsftSkipEx(f"Not enough queues for the test: {ch_max}")
+
+    ethtool(f"-L {cfg.ifname} combined 2")
+    defer(ethtool, f"-L {cfg.ifname} combined {qcnt}")
+
+    ethtool(f"-X {cfg.ifname} weight 1 7")
+    defer(ethtool, f"-X {cfg.ifname} default")
+
+    ethtool(f"-L {cfg.ifname} combined {ch_max}")
+    data = get_rss(cfg)
+    ksft_eq(0, min(data['rss-indirection-table']))
+    ksft_eq(1, max(data['rss-indirection-table']))
+
+    ksft_eq(7,
+            data['rss-indirection-table'].count(1) /
+            data['rss-indirection-table'].count(0),
+            f"Table imbalance after resize: {data['rss-indirection-table']}")
+
+
 def test_rss_context(cfg, ctx_cnt=1, create_with_cfg=None):
     """
     Test separating traffic into RSS contexts.
@@ -442,9 +475,11 @@ def test_rss_context_overlap2(cfg):
 
 def main() -> None:
     with NetDrvEpEnv(__file__, nsim_test=False) as cfg:
+        cfg.ethnl = EthtoolFamily()
         cfg.netdevnl = NetdevFamily()
 
         ksft_run([test_rss_key_indir, test_rss_queue_reconfigure,
+                  test_rss_resize,
                   test_rss_context, test_rss_context4, test_rss_context32,
                   test_rss_context_queue_reconfigure,
                   test_rss_context_overlap, test_rss_context_overlap2,