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SubjectRe: [PATCH 2/8] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode
----- On Nov 28, 2020, at 11:01 AM, Nicholas Piggin 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.



Mathieu Desnoyers
EfficiOS Inc.

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