** Also affects: linux-aws (Ubuntu Groovy)
Importance: Undecided
Status: New
** Also affects: linux-aws (Ubuntu Hirsute)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Description changed:
[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:
http://next.patchew.org/Linux/[email protected]/
+ This is required because various PV features (Async PF, PV EOI, steal
+ time) work through memory shared with hypervisor and when we restore
+ from hibernation we must properly tear down all these features to make
+ sure hypervisor doesn't write to stale locations after we jump to the
+ previously hibernated kernel.
+
+ For this reason it is safe to apply this patch set also to the other
+ generic kernels and not just AWS.
+
[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.
+ This can be easily tested on AWS (but it should be reproduced by
+ hibernating any kvm instance with multiple CPUs). 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:
+ On the AWS kernel replace "UBUNTU: SAUCE: aws: kvm: double the size of
+ hv_clock_boot" with:
http://next.patchew.org/Linux/[email protected]/
+
+ For the other kernels, simply apply this patch set.
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.
** Summary changed:
- aws: proper fix for c5.18xlarge hibernation issues
+ properly tear down KVM PV features on hibernate
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https://bugs.launchpad.net/bugs/1920944
Title:
kvm: properly tear down PV features on hibernate
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