Messages in this thread | | | Date | Fri, 11 Aug 2023 12:21:07 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: mm: use ptep_clear() instead of pte_clear() in clear_flush() |
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On Fri, Aug 11, 2023 at 07:16:20PM +0800, Qi Zheng wrote: > Will Deacon <[1]will@kernel.org>于2023年8月11日 周五19:03写道: > > On Thu, Aug 10, 2023 at 09:32:41AM +0000, Qi Zheng wrote: > > From: Qi Zheng <[2]zhengqi.arch@bytedance.com> > > > > In clear_flush(), the original pte may be a present entry, so we > should > > use ptep_clear() to let page_table_check track the pte clearing > operation, > > otherwise it may cause false positive in subsequent set_pte_at(). > > Isn't this true for most users of pte_clear()? There are some in the > core > code, so could they trigger the false positive as well? > > No, the PTE entry in other places where pte_clear() is used is non-present > PTE. > The page_table_check does not does track the pte operation in this case, > so it will not cause false positives.
Are you sure? For example, the call from flush_all_zero_pkmaps() in highmem.c really looks like it's clearing a valid entry. Not that arm64 cares about highmem, but still.
Will
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