[23.04 FEAT] KVM: Enablement of device busid for subchannels

[bugproxy]

Feature Description

Before kernel 5.15 and libvirt 8.4 it was not possible to know a CCW device bus ID (devno) if the device is unbound from its 'proper' device driver (e.g. dasd-eckd), which is the case if a CCW device is passed through to a KVM guest. This places an unnecessary burden on VM admins, as they have to keep track of the mapping between a subchannel id and the bus id manually, outside of the KVM management stack.
Notes: With kernel 5.15 an additional sysfs property 'dev_busid' was added to the sysfs entry for subchannels which is exposed by libvirt 8.4 and higher. These changes were done in the context of maintainership activities, but with newer libvirt versions included, it makes sense to also include the patch in distro releases.

The commit is
https://github.com/torvalds/linux/commit/d3683c055212bf910d4e318f7944910ce10dbee6

[Frank Heimes (fheimes)]

Okay, since commit d3683c055212 "s390/cio: add dev_busid sysfs entry for each subchannel" got upstream accepted with 5.15 and is still in the lunar master-next tree, I'm updating this ticket to In Progress, since the kernel team is already working on the 6.2 kernel for lunar.

[Frank Heimes (fheimes)]

Since this got upstream accepted with v5.15 - this can be set to Fix Released already now - and btw. not only for lunar (planned target kernel 6.2), but also for kinetic (5.19) as well as for jammy (5.15).