Comment 1 for bug 1791080

This upstream stable update contains the backport for CVE-2018-3639 (x86) aka Spectre v4/SSB.
* x86/cpufeatures: Add CPUID_7_EDX CPUID leaf
  The upstream stable patch adds two previously unknown
  feature bits for word 18 which I added with a SAUCE
  patch.
* x86/cpufeatures: Add Intel feature bits for Speculation
  Control
  -> skip, no change
* x86/cpufeatures: Add AMD feature bits for Speculation
  Control
  -> skip, no change
* x86/msr: Add definitions for new speculation control
  MSRs
  -> skip, no change
* x86/pti: Do not enable PTI on CPUs which are not
  vulnerable to Meltdown
  -> skip, no change
* x86/cpufeature: Blacklist SPEC_CTRL/PRED_CMD on early
  Spectre v2 microcodes
  -> skip, we have actually reverted this at some point
* x86/speculation: Add basic IBPB (Indirect Branch
  Prediction Barrier) support
  -> Picked in reduced form (only adding definition for
     indirect_branch_prediction_barrier(). Not sure this
     will be needed in the end.
* x86/cpufeatures: Clean up Spectre v2 related CPUID
  flags
  -> Mostly can be skipped. Only picking up a small change
     to indirect_branch_prediction_barrier() which is still
     not used.
  Not picking up the firmware blacklist code.
* x86/cpuid: Fix up "virtual" IBRS/IBPB/STIBP feature
  bits on Intel
  -> skipped, no change