** Changed in: ubuntu-z-systems
Status: Triaged => In Progress
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https://bugs.launchpad.net/bugs/1818854
Title:
[Ubuntu] vfio-ap: add subsystem to matrix device to avoid libudev
failures
Status in Ubuntu on IBM z Systems:
In Progress
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Bionic:
New
Status in linux source package in Cosmic:
New
Status in linux source package in Disco:
Fix Committed
Bug description:
SRU Justification:
[Impact]
* The vfio-ap driver will create a matrix device in sysfs without a
subsystem link.
* This causes failures in libudev that might also lead to libvirt
errors.
* A fix is upstream in master branch for kernel 5.1
[Fix]
* 36360658eb5a6cf04bb9f2704d1e4ce54037ec99 3636065 "s390: vfio_ap:
link the vfio_ap devices to the vfio_ap bus subsystem"
[Test Case]
* An s390x machine with at least one CryptoExpress card,
where at least one AP and one 'Domain' is assigned to a particular LPAR.
* Now running virsh nodedev-list before (and later after) construction
the matrix device should expose the issue.
* For details about how to setup a vfio-ap matrix device see:
http://kvmonz.blogspot.com/2018/12/qemu-v31-released.html
(see 2nd bullet: virtio-ap)
[Regression Potential]
* The regression potential can be considered as low since it only
affects the s390x platform
* and there it only affects the usage of AP (CryptoExpress) cards and
it's driver/module
* and again only affects the recently introduced virtual IO function
of AP (vfio-ap).
[Other Info]
* It was already briefly discussed here:
https://www.redhat.com/archives/libvir-list/2019-February/msg00837.html
as well as reviewed and pushed.
* Commit 3636065 from v5.1-rc1
* This affects ccw cards and their vf only, NOT vf of PCI/PCIe cards!
* For details on virtio-ap/vfio-ap see bullet #2 here:
http://kvmonz.blogspot.com/2018/12/qemu-v31-released.html
_________________________
---Problem Description---
The vfio-ap driver will create a matrix device in sysfs without a subsystem
link. This triggers failures in libudev that might also lead to libvirt errors
(e.g. see
https://www.redhat.com/archives/libvir-list/2019-February/msg00837.html)
The proper fix is to add a subsystem link (e.g. by providing a dummy
bus).
A fix for that is upstream in master branch already for kernel 5.1
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=36360658eb5a6cf04bb9f2704d1e4ce54037ec99
This need to be applied to Bionic, Cosmic and Disco
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