Re: [PATCH 2/8] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode

[Mathieu Desnoyers]

----- On Nov 28, 2020, at 11:01 AM, Nicholas Piggin npiggin@xxxxxxxxx wrote:

> And get rid of the generic sync_core_before_usermode facility. This is
> functionally a no-op in the core scheduler code, but it also catches

This sentence is incomplete.

> 
> This helper is the wrong way around I think. The idea that membarrier
> state requires a core sync before returning to user is the easy one
> that does not need hiding behind membarrier calls. The gap in core
> synchronization due to x86's sysret/sysexit and lazy tlb mode, is the
> tricky detail that is better put in x86 lazy tlb code.

Ideally yes this complexity should sit within the x86 architecture code
if only that architecture requires it.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com