Comment 13 for bug 1954680

Hi Harald, glad that you now have a test-system at hand (and thx for the clarification).

Well, so far this LP tickets asks (in LP comment #8: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1954680/comments/7) for verification on hirsute.
focal/20.04 need to be verified soon too, but the 'ubuntu-kernel-bot' did not left a comment regarding focal verification, yet.

I just checked if the code landed in the focal master-next tree:
$ git log --oneline --grep "s390/AP: support new dynamic AP bus size limit"
f65525ab6604 s390/AP: support new dynamic AP bus size limit
and it is and it's tagged to be included in kernel 'Ubuntu-5.4.0-95', which is the next upcoming kernel:
$ git tag --contains f65525ab6604
Ubuntu-5.4.0-95.107

But 'Ubuntu-5.4.0-95' is still in preparation and not yet ready, hence did not arrived in the archives yet (will btw. first land in -proposed):
$ rmadison -a s390x linux-generic | grep focal
 linux-generic | 5.4.0.26.32 | focal | s390x
 linux-generic | 5.4.0.94.98 | focal-security | s390x
 linux-generic | 5.4.0.94.98 | focal-updates | s390x
(-proposed is not yet listed)

So I apologize, that currently on hirsute/21.04 verification is possible (you may just leave the focal system sitting there for a while ...?!)

For hirsute the kernel 5.11.0-47 is the one that incl. the requested patch (according to comment #7) - and I just double checked the hirsute master-next tree:
$ git log --oneline --grep "s390/AP: support new dynamic AP bus size limit"
c0c6e76a5dd8 s390/AP: support new dynamic AP bus size limit
$ git tag --contains c0c6e76a5dd8
Ubuntu-5.11.0-47.52
$ rmadison -a s390x linux-generic | grep hirsute
 linux-generic | 5.11.0.16.17 | hirsute | s390x
 linux-generic | 5.11.0.46.46 | hirsute-security | s390x
 linux-generic | 5.11.0.46.46 | hirsute-updates | s390x
 linux-generic | 5.11.0.47.47 | hirsute-proposed | s390x
So the hirsute kernel is indeed ready to test from proposed (btw. please ignore the right-most digits of the kernel version, they just incl. build info).

And to get a kernel installed and running from the "-proposed" pocket of the archive, the following is needed on top of a standard installation:
1)
enable proposed with:
"sudo add-apt-repository "deb http://us.ports.ubuntu.com/ubuntu-ports/ $(lsb_release -sc)-proposed main"
(for the src use "sudo add-apt-repository "deb-src http://us.ports.ubuntu.com/ubuntu-ports/ $(lsb_release -sc)-proposed main")
2)
Do an "sudo apt update" (if not automatically triggered) and you will find new packages listed by:
"apt list --upgradable"
3)
You can just install all of them (e.g. with "sudo apt full-upgrade"), or just selectively install an updated package, like the kernel (e.g. "sudo apt install linux-generic").
4)
Reboot to activate the new kernel (and check with 'uname' or 'apt-cache policy linux-generic' after reboot and before testing).