From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64/mm: Remove [PUD|PMD]_TABLE_BIT from [pud|pmd]_bad()
Date: Tue, 11 May 2021 09:21:46 +0530 [thread overview]
Message-ID: <4a36d7b7-6b27-31cc-d701-ebe3c6e4946e@arm.com> (raw)
In-Reply-To: <20210510144337.GA92897@C02TD0UTHF1T.local>
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.
> p??_clear_leaf() and p??_none_or_clear_leaf() helpers.
Could you please elaborate how these new helpers might help define
pxx_bad() ?
>
> Thanks,
> Mark.
>
>> ---
>> This applies on v5.13-rc1.
>>
>> arch/arm64/include/asm/pgtable.h | 5 ++---
>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index 25f5c04b43ce..69f8183bef29 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -509,13 +509,12 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>
>> #define pmd_none(pmd) (!pmd_val(pmd))
>>
>> -#define pmd_bad(pmd) (!(pmd_val(pmd) & PMD_TABLE_BIT))
>> -
>> #define pmd_table(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
>> PMD_TYPE_TABLE)
>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
>> PMD_TYPE_SECT)
>> #define pmd_leaf(pmd) pmd_sect(pmd)
>> +#define pmd_bad(pmd) (!pmd_table(pmd))
>>
>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>> #define pte_leaf_size(pte) (pte_cont(pte) ? CONT_PTE_SIZE : PAGE_SIZE)
>> @@ -602,7 +601,7 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
>> pr_err("%s:%d: bad pmd %016llx.\n", __FILE__, __LINE__, pmd_val(e))
>>
>> #define pud_none(pud) (!pud_val(pud))
>> -#define pud_bad(pud) (!(pud_val(pud) & PUD_TABLE_BIT))
>> +#define pud_bad(pud) (!pud_table(pud))
>> #define pud_present(pud) pte_present(pud_pte(pud))
>> #define pud_leaf(pud) pud_sect(pud)
>> #define pud_valid(pud) pte_valid(pud_pte(pud))
>> --
>> 2.20.1
>>
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next prev parent reply other threads:[~2021-05-11 11:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-10 11:07 [PATCH] arm64/mm: Remove [PUD|PMD]_TABLE_BIT from [pud|pmd]_bad() Anshuman Khandual
2021-05-10 14:43 ` Mark Rutland
2021-05-11 3:51 ` Anshuman Khandual [this message]
2021-05-11 14:07 ` Mark Rutland
2021-05-13 5:14 ` Anshuman Khandual
2021-05-14 10:59 ` Catalin Marinas
2021-05-25 18:58 ` Will Deacon
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