i386: derive '-cpu host' from KVM_GET_SUPPORTED_CPUID
The fact that a host cpu supports a feature doesn't mean that QEMU and KVM
will also support it, yet -cpuid host brings host features wholesale.
We need to whitelist each feature separately to make sure we support it.
This patch adds KVM whitelisting (by simply using KVM_GET_SUPPORTED_CPUID
instead of the CPUID instruction).
Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>