[Bug 209079] CPU 0/KVM: page allocation failure on 5.8 kernel

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https://bugzilla.kernel.org/show_bug.cgi?id=209079

--- Comment #5 from Martin Schrodt (kernel@martin.schrodt.org) ---
Strange things happen sometimes...

What I did (I did only unload/reload the module after config changes, hoping
this would suffice):

- running with "kvm_amd nested=0 avic=1 npt=0" and "kvm_amd nested=0 npt=0" on
5.8.7, all working fine.

- rolling back to the 5.8.5 kernel I had the bug with, and trying the above
combinations -> working fine

- rolling the VM back to a state before changing it to AVIC (reasonably sure
it's the same) -> working fine, on both 5.8.7 and 5.8.5.

Heisenbugs here they come.

Trying to come up with things that I changed since then but did not roll back
yet:

I have a qemu hook, which did the following: 

1) drop caches, 
2) compact memory 
3) create a cpuset for the host and move all tasks there to free the cores
assigned to the VM (which included a flag for memory migration, so that the
processes would have their memory moved to the non VM node) 
4) then let qemu allocate memory

Since then I changed this to move the compacting step after the moving step (my
thought was that *after* moving the memory from node 1 to node 0, there is more
free space on node 1, compaction should yield better results)

Does the error I initially got say anything about *why* the allocation failed?

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