From: Amit Cohen amcohen@nvidia.com

'qos_pfc' test checks PFC behavior. The idea is to limit the traffic using a shaper somewhere in the flow of the packets. In this area, the buffer is smaller than the buffer at the beginning of the flow, so it fills up until there is no more space left. The test configures there PFC which is supposed to notice that the headroom is filling up and send PFC Xoff to indicate the transmitter to stop sending traffic for the priorities sharing this PG.

The Xon/Xoff threshold is auto-configured and always equal to 2*(MTU rounded up to cell size). Even after sending the PFC Xoff packet, traffic will keep arriving until the transmitter receives and processes the PFC packet. This amount of traffic is known as the PFC delay allowance.

Currently the buffer for the delay traffic is configured as 100KB. The MTU in the test is 10KB, therefore the threshold for Xoff is about 20KB. This allows 80KB extra to be stored in this buffer.

8-lane ports use two buffers among which the configured buffer is split, the Xoff threshold then applies to each buffer in parallel.

The test does not take into account the behavior of 8-lane ports, when the ports are configured to 400Gbps with 8 lanes or 800Gbps with 8 lanes, packets are dropped and the test fails.

Check if the relevant ports use 8 lanes, in such case double the size of the buffer, as the headroom is split half-half.

Cc: Shuah Khan shuah@kernel.org Cc: linux-kselftest@vger.kernel.org Fixes: bfa804784e32 ("selftests: mlxsw: Add a PFC test") Signed-off-by: Amit Cohen amcohen@nvidia.com Reviewed-by: Ido Schimmel idosch@nvidia.com Signed-off-by: Petr Machata petrm@nvidia.com --- .../selftests/drivers/net/mlxsw/qos_pfc.sh | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/drivers/net/mlxsw/qos_pfc.sh b/tools/testing/selftests/drivers/net/mlxsw/qos_pfc.sh index 49bef76083b8..0f0f4f05807c 100755 --- a/tools/testing/selftests/drivers/net/mlxsw/qos_pfc.sh +++ b/tools/testing/selftests/drivers/net/mlxsw/qos_pfc.sh @@ -119,6 +119,9 @@ h2_destroy()

switch_create() { + local lanes_swp4 + local pg1_size + # pools # -----

@@ -228,7 +231,20 @@ switch_create() dcb pfc set dev $swp4 prio-pfc all:off 1:on # PG0 will get autoconfigured to Xoff, give PG1 arbitrarily 100K, which # is (-2*MTU) about 80K of delay provision. - dcb buffer set dev $swp4 buffer-size all:0 1:$_100KB + pg1_size=$_100KB + + setup_wait_dev_with_timeout $swp4 + + lanes_swp4=$(ethtool $swp4 | grep 'Lanes:') + lanes_swp4=${lanes_swp4#*"Lanes: "} + + # 8-lane ports use two buffers among which the configured buffer + # is split, so double the size to get twice (20K + 80K). + if [[ $lanes_swp4 -eq 8 ]]; then + pg1_size=$((pg1_size * 2)) + fi + + dcb buffer set dev $swp4 buffer-size all:0 1:$pg1_size

# bridges # -------