linux-kernel - Re: [PATCH V2 2/2] powerpc/mm/autonuma: Switch ppc64 to its own implementeation of saved write

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Message-Id: <87d1elufej.fsf@skywalker.in.ibm.com>
Date:   Tue, 14 Feb 2017 17:56:44 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>, akpm@...ux-foundation.org,
        Rik van Riel <riel@...riel.com>,
        Mel Gorman <mgorman@...hsingularity.net>, paulus@...abs.org,
        benh@...nel.crashing.org
Cc:     linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] powerpc/mm/autonuma: Switch ppc64 to its own implementeation of saved write

Michael Ellerman <mpe@...erman.id.au> writes:

> "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> writes:
>> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> index 0735d5a8049f..8720a406bbbe 100644
>> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> @@ -16,6 +16,9 @@
>>  #include <asm/page.h>
>>  #include <asm/bug.h>
>>  
>> +#ifndef __ASSEMBLY__
>> +#include <linux/mmdebug.h>
>> +#endif
>
> I assume that's for the VM_BUG_ON() you add below. But if so wouldn't
> the #include be better placed in book3s/64/pgtable.h also?

mmu-hash.h has got a hack that is explained below

#ifndef __ASSEMBLY__
#include <linux/mmdebug.h>
#endif
/*
 * This is necessary to get the definition of PGTABLE_RANGE which we
 * need for various slices related matters. Note that this isn't the
 * complete pgtable.h but only a portion of it.
 */
#include <asm/book3s/64/pgtable.h>

This is the only place where we do that book3s/64/pgtable.h include this
way. Everybody should include asm/pgable.h which picks the righ version
based on different config option.

#
>
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index fef738229a68..c684ef6cbd10 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -512,6 +512,32 @@ static inline pte_t pte_mkhuge(pte_t pte)
>>  	return pte;
>>  }
>>  
>> +#define pte_mk_savedwrite pte_mk_savedwrite
>> +static inline pte_t pte_mk_savedwrite(pte_t pte)
>> +{
>> +	/*
>> +	 * Used by Autonuma subsystem to preserve the write bit
>> +	 * while marking the pte PROT_NONE. Only allow this
>> +	 * on PROT_NONE pte
>> +	 */
>> +	VM_BUG_ON((pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_RWX | _PAGE_PRIVILEGED)) !=
>> +		  cpu_to_be64(_PAGE_PRESENT | _PAGE_PRIVILEGED));
>> +	return __pte(pte_val(pte) & ~_PAGE_PRIVILEGED);
>> +}
>> +
>
>
> cheers

-aneesh