Comment 10 for bug 2012763

> So just to update/reconfirm something, qemu-system-amd64 fails on systems with more than
> 288 cores, regardless of how you've configured the KVM Guest.

This really should be a guest size limit, I wonder if the system is picking up any default like "but it could be 384 via hotplugging" that one needs to configure.

@Jeff
Could you - in preparation - please provide the most simple libvirt-xml or qemu commandline that you expect to work but fails when the host count it >288.

> I launched a VM via LXC using qemu and verified that it does only create / attach a single CPU core

They also just use qemu, so that shouldn't be different...
Have you done that test
a) on a different system to check how many CPUs it configures by default?
b) on the 384 cpu system and you are saying "it works with the LXD snaps qemu, but not with the qemu in the Archive"?

If it was (a) that test isn't sufficient as qemu has the concept current and max cpus (available for hot-plug). And the Limit counts against the max-cpus.