[SRU][B][PATCH 0/2] qeth: utilize virtual MAC for Layer2 OSD devices (LP: 1880834)

[frank.heimes at canonical.com]

Buglink: https://bugs.launchpad.net/bugs/1880834

SRU Justification:

[Impact]

* A qeth device on a DPM-managed (HMC) IBM Z machine does not obtain its MAC address for layer2 OSD interfaces from the OSA Network Adapter, instead it uses a random MAC address.

* This can cause connectivity issues in environments where reliable and pre-determined MAC addresses are required, ie. when doing network configuration based on DHCP.

[Fix]

* Backport 1: https://launchpadlibrarian.net/481647649/0001-s390-qeth-improve-fallback-to-random-MAC-address.patch

* Backport 2: https://launchpadlibrarian.net/481647657/0002-s390-qeth-utilize-virtual-MAC-for-Layer2-OSD-devices.patch

[Test Case]

* Bring up a qeth L2 OSD interface in DPM-managed (HMC) LPAR

* Inspect the interface's MAC address. It should be the same as displayed in the HMC DPM panels.

* Due to the fact that a system is needed where the HMC is in DPM moce (rather than in classic mode) this needs to be tested by IBM.

[Regression Potential] 

* There is a certain risk for a regression, since OSA devices are the standard netweork devices on s390x.

* But static network configurations are still more popular for the usually long running workload on s390x and not dynamic assignments.

* On the other hand qeth devices are s390x only, so this will at least not affect common code or code for other architectures.

* The modifications are limited to drivers/s390/net/qeth_*.

* The patches are upstream since quite a while, which speaks for their stability.

[Other Info]

* The upstream patch 21b1702af12e "s390/qeth: improve fallback to random MAC address" got upstream accepted with 4.18, hence is already in all Ubuntu release that are newer than bionic

* And the upstream patch b144b99fff69 "s390/qeth: utilize virtual MAC for Layer2 OSD devices" got upstream accepted with 5.0, hence is also already in all Ubuntu release that are newer than bionic.

Julian Wiedmann (2):
  s390/qeth: improve fallback to random MAC address
  s390/qeth: utilize virtual MAC for Layer2 OSD devices

 drivers/s390/net/qeth_core.h      |  3 ++-
 drivers/s390/net/qeth_core_main.c | 14 +++++++-------
 drivers/s390/net/qeth_core_mpc.h  | 27 +++++++++++++++++----------
 drivers/s390/net/qeth_l2_main.c   | 31 +++++++++++++++++--------------
 4 files changed, 43 insertions(+), 32 deletions(-)

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2.25.1