The charm supports settings the cpu-model (deprecated), cpu-models
(preferred), cpu-model-extra-flags (advanced).

Nova is pretty straightforward in listing which CPU it can use, as it
will basically create a CPU config with each cpu inputted + features,
and check via libvirt if these featureset are available on the host cpu.

Now, where this could hurt, is how the host CPU is detected, where nova
is building the host CPU from a simple `get_capabilities`. I've attached
a straightforward script that'll output what Nova will consider the host
CPU.

If Libvirt does not recognize the host as a Sapphire CPU, then Nova
might not see the right featureset (from libvirt calls).

Moreover, the charm supports the config option
`skip_cpu_compare_at_startup`, to prevent nova-compute to check if the
inputted models are compatible and hard exit.
(`skip_cpu_compare_on_dest` with the companion setting to not fail
migrations) (I'm not specifically recommending to turn it on, but it can
be an alternative to running ansible playbooks to modify xml cpu maps on
each compute)

** Attachment added: "get_cpu.py"
   
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/2084102/+attachment/5926576/+files/get_cpu.py

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https://bugs.launchpad.net/bugs/2084102

Title:
  Sapphire rapids not recognized by virsh capabilities

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