Messages in this thread | | | Date | Tue, 11 May 2021 15:07:08 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64/mm: Remove [PUD|PMD]_TABLE_BIT from [pud|pmd]_bad() |
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On Tue, May 11, 2021 at 09:21:46AM +0530, Anshuman Khandual wrote: > > On 5/10/21 8:13 PM, Mark Rutland wrote: > > On Mon, May 10, 2021 at 04:37:51PM +0530, Anshuman Khandual wrote: > >> Semantics wise, [pud|pmd]_bad() have always implied that a given [PUD|PMD] > >> entry does not have a pointer to the next level page table. This had been > >> made clear in the commit a1c76574f345 ("arm64: mm: use *_sect to check for > >> section maps"). Hence explicitly check for a table entry rather than just > >> testing a single bit. This basically redefines [pud|pmd]_bad() in terms of > >> [pud|pmd]_table() making the semantics clear. > >> > >> Cc: Catalin Marinas <catalin.marinas@arm.com> > >> Cc: Will Deacon <will@kernel.org> > >> Cc: Mark Rutland <mark.rutland@arm.com> > >> Cc: linux-arm-kernel@lists.infradead.org > >> Cc: linux-kernel@vger.kernel.org > >> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > > > > I have no strong feelings either way, so: > > > > Acked-by: Mark Rutland <mark.rutland@arm.com> > > > > ... that said, I think that the "bad" naming is unclear and misleading, > > and it'd be really nice if we could clean that up treewide with > > something clearer than "bad". > > Agreed, the name is misleading. > > > It does seem that would roughly fit p??_leaf() if we had > > But what if the platform does not support huge page aka leaf mapping > at the given level ? Also a non table i.e bad entry might not always > mean a leaf/section/huge page mapping, it could simply imply that the > entry is not just pointing to next level and might be just in an bad > intermediate or invalid state.
Ah, so that's also covering swap entries, too? It's not entirely clear to me what "bad intermediate or invalid state" means, because I assume it's not arbitrary junk or this wouldn't be sound genrally.
I had assumed it was only covering *valid* non-table entries.
> > p??_clear_leaf() and p??_none_or_clear_leaf() helpers. > > Could you please elaborate how these new helpers might help define > pxx_bad() ?
This was based on my (evidently wrong) prior understanding above.
Thanks, Mark.
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