Merge tag 'x86_bugs_post_ibpb' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Merge tag 'x86_bugs_post_ibpb' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 IBPB fixes from Borislav Petkov:
 "This fixes the IBPB implementation of older AMDs (< gen4) that do not
  flush the RSB (Return Address Stack) so you can still do some leaking
  when using a "=ibpb" mitigation for Retbleed or SRSO. Fix it by doing
  the flushing in software on those generations.

  IBPB is not the default setting so this is not likely to affect
  anybody in practice"

* tag 'x86_bugs_post_ibpb' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/bugs: Do not use UNTRAIN_RET with IBPB on entry
  x86/bugs: Skip RSB fill at VMEXIT
  x86/entry: Have entry_ibpb() invalidate return predictions
  x86/cpufeatures: Add a IBPB_NO_RET BUG flag
  x86/cpufeatures: Define X86_FEATURE_AMD_IBPB_RET