[UBUNTU 22.04] KVM: s390: unhandled guest LPSWEY instruction

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Description: KVM: s390: unhandled guest LPSWEY instruction

Symptom: guest kernel oops on LPSWEY instruction

Problem: in rare cases like machine check injection with
               PSW disabled, all load PSW instructions are
               intercepted. LPSW and LPSWE are handled by KVM but
               not the new LPSWEY

Solution: Provide an LPSWEY handler in KVM.

Reproduction: hotplug a device while a CPU is disabled for machine
               checks, e.g. during early boot

Upstream-ID: 4c6abb7f7b349f00c0f7ed5045bf67759c012892

Preventive: yes
Reported: upstream
Component: kernel

[Frank Heimes (fheimes)]

Would it be possible to get a test case aka reproducer on this (so forcing the system into such a rare case)? Since we would need a kind of a test for a potential SRU.

[Frank Heimes (fheimes)]

I unfortunately don't see that 4c6abb7f7b34 "KVM: s390: fix LPSWEY handling" got upstream marked as stable update, since in such a case it would have been picked by the Canonical kernel team automatically.

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2024-07-10 06:48 EDT-------
The bug was introduced with kernel 5.14

The available patch (see upstream-ID in comment above) has been added to stable for 5.15. which should help to get picked up by Jammy and later releases.

[Frank Heimes (fheimes)]

Great, that it was added to stable 5.15 - thx!

(In the upstream commit I only found:
Fixes: a3efa8429266 ("KVM: s390: gen_facilities: allow facilities 165, 193, 194 and 196")
would have also assumed to see a line starting with:
Cc: <email address hidden> # ...

But anyway, very happy that it comes to 5.15 via upstream !)