linux-kernel - Re: [PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions

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Message-ID: <85b20d93-bb60-b9e2-ea6a-92ca6f90abc6@arm.com>
Date:   Wed, 24 Jul 2019 14:03:58 +0100
From:   Steven Price <steven.price@....com>
To:     Paul Burton <paul.burton@...s.com>
Cc:     Mark Rutland <Mark.Rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "H. Peter Anvin" <hpa@...or.com>, Will Deacon <will@...nel.org>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        James Hogan <jhogan@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Jérôme Glisse <jglisse@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Morse <james.morse@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions

On 22/07/2019 22:47, Paul Burton wrote:
> Hi Steven,
> 
> On Mon, Jul 22, 2019 at 04:41:53PM +0100, Steven Price wrote:
>> 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 mips, we only support large pages on 64 bit.
> 
> That ceases to be true with commit 35476311e529 ("MIPS: Add partial
> 32-bit huge page support") in mips-next, so I think it may be best to
> move the definition to asm/pgtable.h so that both 32b & 64b kernels can
> pick it up.

Thanks for pointing that out. I'll move the definitions as you suggest.

Steve

> Thanks,
>     Paul
> 
>> For 64 bit if _PAGE_HUGE is defined we can simply look for it. When not
>> defined we can be confident that there are no leaf pages in existence
>> and fall back on the generic implementation (added in a later patch)
>> which returns 0.
>>
>> CC: Ralf Baechle <ralf@...ux-mips.org>
>> CC: Paul Burton <paul.burton@...s.com>
>> CC: James Hogan <jhogan@...nel.org>
>> CC: linux-mips@...r.kernel.org
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>>  arch/mips/include/asm/pgtable-64.h | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
>> index 93a9dce31f25..2bdbf8652b5f 100644
>> --- a/arch/mips/include/asm/pgtable-64.h
>> +++ b/arch/mips/include/asm/pgtable-64.h
>> @@ -273,6 +273,10 @@ static inline int pmd_present(pmd_t pmd)
>>  	return pmd_val(pmd) != (unsigned long) invalid_pte_table;
>>  }
>>  
>> +#ifdef _PAGE_HUGE
>> +#define pmd_leaf(pmd)	((pmd_val(pmd) & _PAGE_HUGE) != 0)
>> +#endif
>> +
>>  static inline void pmd_clear(pmd_t *pmdp)
>>  {
>>  	pmd_val(*pmdp) = ((unsigned long) invalid_pte_table);
>> @@ -297,6 +301,10 @@ static inline int pud_present(pud_t pud)
>>  	return pud_val(pud) != (unsigned long) invalid_pmd_table;
>>  }
>>  
>> +#ifdef _PAGE_HUGE
>> +#define pud_leaf(pud)	((pud_val(pud) & _PAGE_HUGE) != 0)
>> +#endif
>> +
>>  static inline void pud_clear(pud_t *pudp)
>>  {
>>  	pud_val(*pudp) = ((unsigned long) invalid_pmd_table);
>> -- 
>> 2.20.1
>>
> 
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> 

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