Merge tag 'powerpc-spectre-rsb' of powerpc-CVE-2019-18660.bundle

Pull powerpc Spectre-RSB fixes from Michael Ellerman:
 "We failed to activate the mitigation for Spectre-RSB (Return Stack
  Buffer, aka. ret2spec) on context switch, on CPUs prior to Power9
  DD2.3.

  That allows a process to poison the RSB (called Link Stack on Power
  CPUs) and possibly misdirect speculative execution of another process.
  If the victim process can be induced to execute a leak gadget then it
  may be possible to extract information from the victim via a side
  channel.

  The fix is to correctly activate the link stack flush mitigation on
  all CPUs that have any mitigation of Spectre v2 in userspace enabled.

  There's a second commit which adds a link stack flush in the KVM guest
  exit path. A leak via that path has not been demonstrated, but we
  believe it's at least theoretically possible.

  This is the fix for CVE-2019-18660"

* tag 'powerpc-spectre-rsb' of /home/torvalds/Downloads/powerpc-CVE-2019-18660.bundle:
  KVM: PPC: Book3S HV: Flush link stack on guest exit to host kernel
  powerpc/book3s64: Fix link stack flush on context switch

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