Messages in this thread | | | Date | Tue, 22 Aug 2023 10:58:47 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: mm: use ptep_clear() instead of pte_clear() in clear_flush() |
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On Mon, Aug 21, 2023 at 01:21:19PM -0700, Andrew Morton wrote: > On Fri, 11 Aug 2023 19:28:41 +0800 Qi Zheng <zhengqi.arch@bytedance.com> wrote: > > > Will Deacon <will@kernel.org>于2023年8月11日 周五19:21写道: > > > > > 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. > > > > > > Ah, this is init_mm, not user mm, page_table_check does not care about this > > case. > > It's unclear where we stand with this patch. An ack or a nack, please?
Sorry Andrew, I saw you'd queued it so I marked it as "done" on my list. I think it's fine:
Acked-by: Will Deacon <will@kernel.org>
Will
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