Re: [PATCH] LoongArch: let pmd_present return true when splitting pmd
From: bibo, mao
Date: Tue Jun 06 2023 - 22:57:38 EST
I suggest to using bit12-bit20 since high weight bits such 63-61 are hw bits, it may
expand for future hw use, or you had better negotiate with hw guys.
>>> +#define _PAGE_PRESENT_INVALID_SHIFT 60
>>> #define _PAGE_NO_READ_SHIFT 61
>>> #define _PAGE_NO_EXEC_SHIFT 62
>>> #define _PAGE_RPLV_SHIFT 63
Regards
Bibo, Mao
在 2023/6/6 21:49, bibo, mao 写道:
> I do not object to adding sw bit for _PAGE_PRESENT_INVALID, only that can it use
> bit12--bit20 since it is for pmd entry only?
>
> Regards
> Bibo, Mao
>
> 在 2023/6/6 19:38, Hongchen Zhang 写道:
>> Hi,
>>
>> Gentle ping.
>>
>> On 2023/5/24 pm 3:41, Hongchen Zhang wrote:
>>> when we split a pmd into ptes, pmd_present() and pmd_trans_huge() should
>>> return true,otherwise it would be treated as a swap pmd.
>>> As arm64 does in
>>> commit b65399f6111b ("arm64/mm: Change THP helpers to comply with generic MM semantics")
>>> we add a _PAGE_PRESENT_INVALID bit for LoongArch.
>>>
>>> Signed-off-by: Hongchen Zhang <zhanghongchen@xxxxxxxxxxx>
>>> ---
>>> arch/loongarch/include/asm/pgtable-bits.h | 2 ++
>>> arch/loongarch/include/asm/pgtable.h | 3 ++-
>>> 2 files changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/loongarch/include/asm/pgtable-bits.h b/arch/loongarch/include/asm/pgtable-bits.h
>>> index 8b98d22a145b..a7469d28d9d0 100644
>>> --- a/arch/loongarch/include/asm/pgtable-bits.h
>>> +++ b/arch/loongarch/include/asm/pgtable-bits.h
>>> @@ -22,12 +22,14 @@
>>> #define _PAGE_PFN_SHIFT 12
>>> #define _PAGE_SWP_EXCLUSIVE_SHIFT 23
>>> #define _PAGE_PFN_END_SHIFT 48
>>> +#define _PAGE_PRESENT_INVALID_SHIFT 60
>>> #define _PAGE_NO_READ_SHIFT 61
>>> #define _PAGE_NO_EXEC_SHIFT 62
>>> #define _PAGE_RPLV_SHIFT 63
>>> /* Used by software */
>>> #define _PAGE_PRESENT (_ULCAST_(1) << _PAGE_PRESENT_SHIFT)
>>> +#define _PAGE_PRESENT_INVALID (_ULCAST_(1) << _PAGE_PRESENT_INVALID_SHIFT)
>>> #define _PAGE_WRITE (_ULCAST_(1) << _PAGE_WRITE_SHIFT)
>>> #define _PAGE_ACCESSED (_ULCAST_(1) << _PAGE_ACCESSED_SHIFT)
>>> #define _PAGE_MODIFIED (_ULCAST_(1) << _PAGE_MODIFIED_SHIFT)
>>> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
>>> index d28fb9dbec59..9a9f9ff9b709 100644
>>> --- a/arch/loongarch/include/asm/pgtable.h
>>> +++ b/arch/loongarch/include/asm/pgtable.h
>>> @@ -213,7 +213,7 @@ static inline int pmd_bad(pmd_t pmd)
>>> static inline int pmd_present(pmd_t pmd)
>>> {
>>> if (unlikely(pmd_val(pmd) & _PAGE_HUGE))
>>> - return !!(pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE));
>>> + return !!(pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PRESENT_INVALID));
>>> return pmd_val(pmd) != (unsigned long)invalid_pte_table;
>>> }
>>> @@ -558,6 +558,7 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
>>> static inline pmd_t pmd_mkinvalid(pmd_t pmd)
>>> {
>>> + pmd_val(pmd) |= _PAGE_PRESENT_INVALID;
>>> pmd_val(pmd) &= ~(_PAGE_PRESENT | _PAGE_VALID | _PAGE_DIRTY | _PAGE_PROTNONE);
>>> return pmd;
>>>
>>> base-commit: f1fcbaa18b28dec10281551dfe6ed3a3ed80e3d6
>>>
>>
>> Best Regards
>> Hongchen Zhang
>>
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