Re: [RFC PATCH 1/2] x86/ibpb: Skip IBPB when we switch back to same user process

[Arjan van de Ven]

> This means that 'A -> idle -> A' should never pass through switch_mm to
> begin with.
>
> Please clarify how you think it does.

the idle code does leave_mm() to avoid having to IPI CPUs in deep sleep states
for a tlb flush.

(trust me, that you really want, sequentially IPI's a pile of cores in a deep sleep
state to just flush a tlb that's empty, the performance of that is horrific)