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Subject: Re: [PATCH v16 06/25] powerpc: mm: Add p?d_leaf() definitions
To: Michael Ellerman <mpe@ellerman.id.au>,
 Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
References: <20191206135316.47703-1-steven.price@arm.com>
 <20191206135316.47703-7-steven.price@arm.com>
 <875ziprc27.fsf@mpe.ellerman.id.au>
From: Steven Price <steven.price@arm.com>
Message-ID: <6dec1a22-963a-226e-c7c8-c445daa35d29@arm.com>
Date: Mon, 9 Dec 2019 13:06:26 +0000
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Cc: Mark Rutland <Mark.Rutland@arm.com>, Peter Zijlstra <peterz@infradead.org>,
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On 09/12/2019 11:08, Michael Ellerman wrote:
> Steven Price <steven.price@arm.com> writes:
>> walk_page_range() is going to be allowed to walk page tables other than
>> those of user space. For this it needs to know when it has reached a
>> 'leaf' entry in the page tables. This information is provided by the
>> p?d_leaf() functions/macros.
>>
>> For powerpc pmd_large() already exists and does what we want, so hoist
>> it out of the CONFIG_TRANSPARENT_HUGEPAGE condition and implement the
>> other levels. Macros are used to provide the generic p?d_leaf() names.
>>
>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> CC: Paul Mackerras <paulus@samba.org>
>> CC: Michael Ellerman <mpe@ellerman.id.au>
>> CC: linuxppc-dev@lists.ozlabs.org
>> CC: kvm-ppc@vger.kernel.org
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>  arch/powerpc/include/asm/book3s/64/pgtable.h | 30 ++++++++++++++------
>>  1 file changed, 21 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index b01624e5c467..3dd7b6f5edd0 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -923,6 +923,12 @@ static inline int pud_present(pud_t pud)
>>  	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT));
>>  }
>>  
>> +#define pud_leaf	pud_large
>> +static inline int pud_large(pud_t pud)
>> +{
>> +	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
>> +}
> 
> We already have:
> 
> #define pud_is_leaf pud_is_leaf
> static inline bool pud_is_leaf(pud_t pud)
> {
> 	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
> }
> 
> And so on.
> 
> These went in relatively recently in:
> 
>   d6eacedd1f0e ("powerpc/book3s: Use config independent helpers for page table walk")
> 
> 
> Assuming those all work for you, maybe your patch in this series should
> just do:
> 
> #define pud_leaf pud_is_leaf
> 
> And so on. And then we can do a patch later to change the arch/powerpc
> code to use pud_leaf() etc. directly and drop the "is" versions.

Thanks for pointing this out - these didn't exist when I started this
patch series, but yes it would be a good idea to make use of them now.
Followed by cleaning up to use the shorter p?d_leaf() versions in a
later patch.

Thanks,

Steve

> cheers
> 
> 
>> @@ -966,6 +972,12 @@ static inline int pgd_present(pgd_t pgd)
>>  	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT));
>>  }
>>  
>> +#define pgd_leaf	pgd_large
>> +static inline int pgd_large(pgd_t pgd)
>> +{
>> +	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
>> +}
>> +
>>  static inline pte_t pgd_pte(pgd_t pgd)
>>  {
>>  	return __pte_raw(pgd_raw(pgd));
>> @@ -1133,6 +1145,15 @@ static inline bool pmd_access_permitted(pmd_t pmd, bool write)
>>  	return pte_access_permitted(pmd_pte(pmd), write);
>>  }
>>  
>> +#define pmd_leaf	pmd_large
>> +/*
>> + * returns true for pmd migration entries, THP, devmap, hugetlb
>> + */
>> +static inline int pmd_large(pmd_t pmd)
>> +{
>> +	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
>> +}
>> +
>>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>  extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
>>  extern pmd_t mk_pmd(struct page *page, pgprot_t pgprot);
>> @@ -1159,15 +1180,6 @@ pmd_hugepage_update(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp,
>>  	return hash__pmd_hugepage_update(mm, addr, pmdp, clr, set);
>>  }
>>  
>> -/*
>> - * returns true for pmd migration entries, THP, devmap, hugetlb
>> - * But compile time dependent on THP config
>> - */
>> -static inline int pmd_large(pmd_t pmd)
>> -{
>> -	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
>> -}
>> -
>>  static inline pmd_t pmd_mknotpresent(pmd_t pmd)
>>  {
>>  	return __pmd(pmd_val(pmd) & ~_PAGE_PRESENT);
>> -- 
>> 2.20.1
> 
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