[PATCH net-next] selftests: drv-net: toeplitz: cap the Rx queue count

[Jakub Kicinski <kuba@kernel.org>]

The RPS test needs a free CPU within the first RPS_MAX_CPUS (16)
cores. This is easily violated if the NIC or env allocates the
IRQs to cores linearly.

Cap the Rx queues at 8, we don't need more. This makes the test
pass on CX7 in NIPA.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: shuah@kernel.org
CC: willemb@google.com
CC: noren@nvidia.com
CC: gal@nvidia.com
CC: linux-kselftest@vger.kernel.org
---
 .../selftests/drivers/net/hw/toeplitz.py      | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/hw/toeplitz.py b/tools/testing/selftests/drivers/net/hw/toeplitz.py
index cd7e080e6f84..571732198b93 100755
--- a/tools/testing/selftests/drivers/net/hw/toeplitz.py
+++ b/tools/testing/selftests/drivers/net/hw/toeplitz.py
@@ -21,6 +21,8 @@ from lib.py import ksft_variants, KsftNamedVariant, KsftSkipEx, KsftFailEx
 ETH_RSS_HASH_TOP = 1
 # Must match RPS_MAX_CPUS in toeplitz.c
 RPS_MAX_CPUS = 16
+# Cap Rx queues so IRQ pinning leaves free CPUs in the RPS_MAX_CPUS range
+QUEUE_CAP = 8
 
 
 def _check_rps_and_rfs_not_configured(cfg):
@@ -48,6 +50,25 @@ RPS_MAX_CPUS = 16
         return int(data)
 
 
+def _cap_queue_count(cfg):
+    ehdr = {"header": {"dev-index": cfg.ifindex}}
+    chans = cfg.ethnl.channels_get(ehdr)
+
+    config = {}
+    restore = {}
+    for key in ("combined-count", "rx-count"):
+        cur = chans.get(key, 0)
+        if cur > QUEUE_CAP:
+            config[key] = QUEUE_CAP
+            restore[key] = cur
+
+    if not config:
+        return
+
+    cfg.ethnl.channels_set(ehdr | config)
+    defer(cfg.ethnl.channels_set, ehdr | restore)
+
+
 def _get_irq_cpus(cfg):
     """
     Read the list of IRQs for the device Rx queues.
@@ -177,6 +198,7 @@ RPS_MAX_CPUS = 16
     ]
 
     if grp:
+        _cap_queue_count(cfg)
         _check_rps_and_rfs_not_configured(cfg)
     if grp == "rss":
         irq_cpus = ",".join([str(x) for x in _get_irq_cpus(cfg)])
-- 
2.54.0