[SRU][F/aws][PATCH 0/2] aws: proper fix for c5.18xlarge hibernation issues

[Andrea Righi]

BugLink: https://bugs.launchpad.net/bugs/1920944

[Impact]

In LP: #1918694 we applied a fix and a workaround to solve the
hibernation issues on c5.18xlarge. The workaround was in the form of a
SAUCE patch:

  "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot"

It looks like we can replace this workaround with a proper fix, by
applying this patch:
https://lore.kernel.org/kvm/87sg4t7vqy.fsf@vitty.brq.redhat.com/T/#m7533e1d1e551bff425da029fd401bd87935edc33

[Test plan]

Create a c5.18xlarge instance, run the memory stress test script (the
same test script that we are using to stress test hibernation), trigger
the hibernate event, trigger the resume event. Repeat a couple of times
and the problem is very likely to happen.

[Fix]

Replace "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot"
with:

https://lore.kernel.org/kvm/87sg4t7vqy.fsf@vitty.brq.redhat.com/T/#m7533e1d1e551bff425da029fd401bd87935edc33

The fix has been tested extensively in the AWS infrastructure with
positive results.

[Regression potential]

This new code introduced by the fix can be executed also when a CPU is
put offline, so we may see potential regressions in the KVM CPU
hotplugging.