[PATCH v3 3/3] selftests: net: add a virtio_net deadlock selftest

[Bui Quang Minh]

The selftest reproduces the deadlock scenario when binding/unbinding XDP
program, XDP socket, rx ring resize on virtio_net interface.

Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx>
---
 tools/testing/selftests/Makefile              |  2 +-
 .../selftests/drivers/net/virtio_net/Makefile |  2 +
 .../selftests/drivers/net/virtio_net/config   |  1 +
 .../drivers/net/virtio_net/lib/py/__init__.py | 16 ++++++
 .../drivers/net/virtio_net/xsk_pool.py        | 52 +++++++++++++++++++
 5 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/drivers/net/virtio_net/lib/py/__init__.py
 create mode 100755 tools/testing/selftests/drivers/net/virtio_net/xsk_pool.py

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index c77c8c8e3d9b..0a6b096f98b7 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -130,7 +130,7 @@ TARGETS_HOTPLUG = cpu-hotplug
 TARGETS_HOTPLUG += memory-hotplug
 
 # Networking tests want the net/lib target, include it automatically
-ifneq ($(filter net drivers/net drivers/net/hw,$(TARGETS)),)
+ifneq ($(filter net drivers/net drivers/net/hw drivers/net/virtio_net,$(TARGETS)),)
 ifeq ($(filter net/lib,$(TARGETS)),)
 	INSTALL_DEP_TARGETS := net/lib
 endif
diff --git a/tools/testing/selftests/drivers/net/virtio_net/Makefile b/tools/testing/selftests/drivers/net/virtio_net/Makefile
index 7ec7cd3ab2cc..82adda96ef15 100644
--- a/tools/testing/selftests/drivers/net/virtio_net/Makefile
+++ b/tools/testing/selftests/drivers/net/virtio_net/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0+ OR MIT
 
 TEST_PROGS = basic_features.sh \
+        xsk_pool.py \
         #
 
 TEST_FILES = \
@@ -8,6 +9,7 @@ TEST_FILES = \
         #
 
 TEST_INCLUDES = \
+        $(wildcard lib/py/*.py ../lib/py/*.py) \
         ../../../net/forwarding/lib.sh \
         ../../../net/lib.sh \
         #
diff --git a/tools/testing/selftests/drivers/net/virtio_net/config b/tools/testing/selftests/drivers/net/virtio_net/config
index bcf7555eaffe..12e8caa22613 100644
--- a/tools/testing/selftests/drivers/net/virtio_net/config
+++ b/tools/testing/selftests/drivers/net/virtio_net/config
@@ -6,3 +6,4 @@ CONFIG_NET_L3_MASTER_DEV=y
 CONFIG_NET_VRF=m
 CONFIG_VIRTIO_DEBUG=y
 CONFIG_VIRTIO_NET=y
+CONFIG_XDP_SOCKETS=y
diff --git a/tools/testing/selftests/drivers/net/virtio_net/lib/py/__init__.py b/tools/testing/selftests/drivers/net/virtio_net/lib/py/__init__.py
new file mode 100644
index 000000000000..b582885786f5
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/virtio_net/lib/py/__init__.py
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0
+
+import sys
+from pathlib import Path
+
+KSFT_DIR = (Path(__file__).parent / "../../../../..").resolve()
+
+try:
+    sys.path.append(KSFT_DIR.as_posix())
+    from net.lib.py import *
+    from drivers.net.lib.py import *
+except ModuleNotFoundError as e:
+    ksft_pr("Failed importing `net` library from kernel sources")
+    ksft_pr(str(e))
+    ktap_result(True, comment="SKIP")
+    sys.exit(4)
diff --git a/tools/testing/selftests/drivers/net/virtio_net/xsk_pool.py b/tools/testing/selftests/drivers/net/virtio_net/xsk_pool.py
new file mode 100755
index 000000000000..3f80afd97d4e
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/virtio_net/xsk_pool.py
@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+# This is intended to be run on a virtio-net guest interface.
+# The test binds the XDP socket to the interface without setting
+# the fill ring to trigger delayed refill_work. This helps to
+# make it easier to reproduce the deadlock when XDP program,
+# XDP socket bind/unbind, rx ring resize race with refill_work on
+# the buggy kernel.
+
+from lib.py import ksft_exit, ksft_run
+from lib.py import KsftSkipEx, KsftFailEx
+from lib.py import NetDrvEnv
+from lib.py import bkg, ip, cmd, ethtool
+import re
+
+def _get_rx_ring_entries(cfg):
+    output = ethtool(f"-g {cfg.ifname}").stdout
+    values = re.findall(r'RX:\s+(\d+)', output)
+    return int(values[1])
+
+def setup_xsk(cfg, xdp_queue_id = 0) -> bkg:
+    # Probe for support
+    xdp = cmd(f'{cfg.net_lib_dir / "xdp_helper"} - -', fail=False)
+    if xdp.ret == 255:
+        raise KsftSkipEx('AF_XDP unsupported')
+    elif xdp.ret > 0:
+        raise KsftFailEx('unable to create AF_XDP socket')
+
+    return bkg(f'{cfg.net_lib_dir / "xdp_helper"} {cfg.ifindex} {xdp_queue_id}',
+               ksft_wait=3)
+
+def check_xdp_bind(cfg):
+    ip(f"link set dev %s xdp obj %s sec xdp" %
+       (cfg.ifname, cfg.net_lib_dir / "xdp_dummy.bpf.o"))
+    ip(f"link set dev %s xdp off" % cfg.ifname)
+
+def check_rx_resize(cfg, queue_size = 128):
+    rx_ring = _get_rx_ring_entries(cfg)
+    ethtool(f"-G %s rx %d" % (cfg.ifname, queue_size))
+    ethtool(f"-G %s rx %d" % (cfg.ifname, rx_ring))
+
+def main():
+    with NetDrvEnv(__file__, nsim_test=False) as cfg:
+        xsk_bkg = setup_xsk(cfg)
+
+        ksft_run([check_xdp_bind, check_rx_resize],
+                 args=(cfg, ))
+    ksft_exit()
+
+if __name__ == "__main__":
+    main()
-- 
2.43.0