On Thu, Aug 18, 2022 at 02:34:45PM +0800, Huang, Ying wrote: > > In this specific case, the only way to do safe tlb batching in my mind is: > > > > pte_offset_map_lock(); > > arch_enter_lazy_mmu_mode(); > > // If any pending tlb, do it now > > if (mm_tlb_flush_pending()) > > flush_tlb_range(vma, start, end); > > else > > flush_tlb_batched_pending(); > > I don't think we need the above 4 lines. Because we will flush TLB > before we access the pages. Could you elaborate? > Can you find any issue if we don't use the above 4 lines? It seems okay to me to leave stall tlb at least within the scope of this function. It only collects present ptes and flush propoerly for them. I don't quickly see any other implications to other not touched ptes - unlike e.g. mprotect(), there's a strong barrier of not allowing further write after mprotect() returns. Still I don't know whether there'll be any side effect of having stall tlbs in !present ptes because I'm not familiar enough with the private dev swap migration code. But I think having them will be safe, even if redundant. Thanks, -- Peter Xu
