MFC r262338
  When the kernel is running in a virtual machine, it cannot rely upon the
  processor family to determine if the workaround for AMD Family 10h Erratum
  383 should be enabled.  To enable virtual machine migration among a
  heterogeneous collection of physical machines, the hypervisor may have
  been configured to report an older processor family with a reduced feature
  set.  Effectively, the reported processor family and its features are like
  a "least common denominator" for the collection of machines.

  Therefore, when the kernel is running in a virtual machine, instead of
  relying upon the processor family, we now test for features that prove
  that the underlying processor is not affected by the erratum.  (The
  features that we test for are unlikely to ever be emulated in software
  on an affected physical processor.)

PR:		186061