[SRU][F][G][PATCH 0/1 v2] net/mlx5e: Add missing capability check for uplink follow (LP: 1921104)

[frank.heimes at canonical.com]

BugLink: https://bugs.launchpad.net/bugs/1921104

SRU Justification:

[Impact]

* Since older firmware may not support the uplink state setting, this can lead to problems.

* Now expose firmware indication that it supports setting eswitch uplink state to follow the physical link.

* If a kernel without the backport is used on an adapter which does not have the latest adapter firmware, the adapter silently drops outgoing traffic.

* This is a regression which was introduced with kernel 5.4.0-48.

[Fix]

* upstream fix (as in 5.11):
  9c9be85f6b59d80efe4705109c0396df18d4e11d 9c9be85f6b59 "net/mlx5e: Add missing capability check for uplink follow"

* backport for focal: https://launchpadlibrarian.net/529543695/0001-Backport-net-mlx5e-Add-missing-capability-check-for-.patch

* backport for groovy: https://launchpadlibrarian.net/529775887/0001-Backport-groovy-net-mlx5e-Add-missing-capability-che.patch

[Test Case]

* Two IBM Z or LinuxONE systems, installed with Ubuntu Server 20.04 or 20.10 on LPAR, are needed.

* Each with RoCE Express 2.x adapters (Mellanox ConnectX4/5) attached and firmware 16.29.1006 or earlier.

* Assign an IP address to the adapters on both systems and try to ping one node from the other.

* The ping will just fail with the stock Ubuntu kernels (not having the patch), but will succeed with kernels that incl. the patches (like the test builds from the PPA mentioned below).

* Due to the lack of hardware this needs to be verified by IBM.

[Regression Potential]

* Undesired / erroneous behavior in case the modified if condition is assembled in a wrong way.

* Again wrong behavior in case the modification of the capability bits in mlx5_ifc_cmd_hca_cap_bits are wrong.

* All modification are limited to the mlx5 driver only.

* The changes are relatively limited with effectively two lines removed and 4 added (three of them adjustments of the capability bits only).

* The modifications were done and tested by IBM and reviewed by Mellanox (see LP comments), based on a PPA test build.

[Other]

* The above patch/commit was upstream accepted with kernel 5.11.

* Hence the patch is not needed for hirsute, just needs to be SRUed for groovy and focal.

* The commit couldn't be cleanly cherry-picked, mainly due to changed context, hence the backport(s).

Alexander Schmidt (1):
  Backport net/mlx5e: Add missing capability check for uplink follow

 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 3 ++-
 include/linux/mlx5/mlx5_ifc.h                     | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

-- 
2.25.1