On Wed, Jan 10, 2018 at 02:10:10PM +0100, Andrea Arcangeli wrote: > It's still incredibly faster to shutdown part of the CPU temporarily > than to flush its internal state as a whole with IBPB. If it wouldn't > be the case ibrs_enabled 0 ibpb_enabled 2 special mode would perform > better (but that's only enabled by default if SPEC_CTRL is not > available and only IBPB_SUPPORT is).
Yet another bit of perhaps useful info: if you run 100% kernel intensive computation (i.e. only interrupts on idle task or a kernel driver doing all in kernel) ibrs_enabled 0 ibpb_enabled 2 of course is much faster than ibrs_enabled 1 ibpb_enabled 1. As long as you don't have frequent ring change, ibrs_enabled 0 ibpb_enabled 2 is faster.
