[pve-devel] [PATCH] enforce cpu check

[Daniel Hunsaker]

> I think that this is impossible to implement, because users may have
different hosts
> inside one cluster. So It is hard to tell what selection we should allow.

We should have the info on the host they're creating it on, which is what I
was thinking about, but it would certainly be tricky to do a lowest common
denominator of the whole cluster.  Though since the CPU features aren't
likely to change often, if at all, we *could* have each host report what it
supports when it joins the cluster, and go from there.  That data could
then be used to prevent creating a VM with a virtual CPU the selected host
doesn't support, migrating a VM to a host that won't be able to run it, and
anything else that might come up as useful to use such data for.

The information itself, namely which instruction set(s) and features a CPU
supports (rather than the make/model of the CPU, which would be
ridiculously overcomplicated to maintain a list for) is readily available
through the proc filesystem (I'll have to look up exactly what the path
is).  So getting that data will be pretty straightforward.  We'd then have
to compile/acquire a list of features needed by each of the virtual CPU
types KVM supports, and it would be a relatively simple matter, from there,
to filter out the ones the current host isn't compatible with.  So long as
it's kept on a strictly per-host basis, this approach should work fairly
well.  Though cluster-wide statistics on what people are actually using
might be nice to have available, too...
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