Comment 3 for bug 1791080

Continue Spectre v4 review:
* x86/speculation: Remove Skylake C2 from Speculation
  Control microcode blacklist
  -> skip, ignore blacklist
* selftest/seccomp: Fix the flag name
  SECCOMP_FILTER_FLAG_TSYNC
  -> skip, no change
* x86/amd: don't set X86_BUG_SYSRET_SS_ATTRS when
  running under Xen
  -> pick, context
* x86/nospec: Simplify alternative_msr_write()
  -> skip, no change
* x86/bugs: Concentrate bug detection into a separate
  function
  -> skip, no change
* x86/bugs: Concentrate bug reporting into a separate
  function
  -> skip, no change (silly patches with near identical
     summary lines)
* x86/bugs: Read SPEC_CTRL MSR during boot and re-use
  reserved bits
  -> skip, but added SAUCE patch to adjust the following
     inline functions to their final upstream stable form
     (as in 4.4.154)
     - indirect_branch_prediction_barrier(),
     - firmware_restrict_branch_speculation_start(),
     - firmware_restrict_branch_speculation_end()
* x86/bugs, KVM: Support the combination of guest and
  host IBRS
  -> skip, no change
* x86/cpu: Rename Merrifield2 to Moorefield
  -> skip, no change
* x86/cpu/intel: Add Knights Mill to Intel family
  -> skip, no change
* x86/bugs: Expose /sys/../spec_store_bypass
  -> skip, add sauce (Initially dropped Knights Mill
     because it was undefined but later added definition
     but not not updated the no ssb array.
* x86/cpufeatures: Add X86_FEATURE_RDS
  -> skip, no change