x86/retpoline: Add feature bit for additional return buffer protections
On Skylake we want additional protections against spectre_v2
over the normal RETPOLINE against underflowing return buffers.
On return buffer underflow the CPU could fall back to
the poisoned indirect branch predictor.
This patch adds a feature bit, only enabled on Skylake,
to enable additional return buffer underflow protections
This will be used in the next patches
Signed-off-by: Andi Kleen <ak@linux.intel.com>
2 files changed
