On Fri, 2018-01-05 at 02:49 -0800, Paul Turner wrote:
> 
> 
> While the potential incompatibility is unfortunate; I'm not sure it makes a
> significant adoption to the adoption rate of CET.

There is no incompatibility. Nothing will have CET that doesn't have
IBRS_ATT (and hence the retpoline alternative'd out into a bare jmp
again).