KVM can't virtualize rdtscp on AMD CPUs yet, so there's no point
in enabling it by default on AMD CPU models, as all we are
getting are confused users because of the "host doesn't support
requested feature" warnings.
Disable rdtscp on Opteron_G* models, but keep compatibility on
pc-*-2.4 and older (just in case there are people are doing funny
stuff using AMD CPU models on Intel hosts).
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
33b5e8c03a