KVM does not really do much with the PAT, so this went unnoticed for a
long time.  It is exposed however if you try to do rdmsr on the PAT
register.
Reported-by: Valentine Sinitsyn <valentine.sinitsyn@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>