[SRU][F][PATCH 0/1] zPCI: Enabling of a reserved PCI function regression introduced by multi-function support (LP: 1891437)

[frank.heimes at canonical.com]

Buglink: https://bugs.launchpad.net/bugs/1891437

SRU Justification:

[Impact]

* If a NVMe drive is assigned/hotplugged to a Linux on s390x LPAR, a bug in lib/list_debug.c is hit and the device is not accessible.

* The reason is a missing /dev/ file -- lspci does not report it either.

[Fix]

* 3047766bc6ec9c6bc9ece85b45a41ff401e8d988 3047766bc6ec "s390/pci: fix enabling a reserved PCI function"

[Test Case]

* Assign a NMVe drive to your LPAR (using the HMC)

* Unassign the NVMe drive from your LPAR

* Reassign it to your LPAR again

* Look at dmesg for 'kernel BUG at lib/list_debug.c'

[Regression Potential]

* There is some regression risk with having code changes in the zPCI sub-system.

* zPCI is the PCI implementation on s390x, modifications here do not affect any other architecture.

* It could be that PCI events do not work anymore and NVMe devices don't IPL (boot) on s390x anymore.

* However, the code changes below to a single file: arch/s390/pci/pci_event.c

* and IPL from NVMe is brand new in Ubuntu for s390x,

* and zPCI devices are less wide-spread compared to ccw devices on s390x.

* On top a test kernel was build and made available for further testing.

[Other]

* Since the fix/patch got upstream accepted with kernel v5.8-rc5, it's already in the groovy proposed kernel 5.8, hence this SRU is for focal only.

Niklas Schnelle (1):
  s390/pci: fix enabling a reserved PCI function

 arch/s390/pci/pci_event.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

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2.25.1