linux-kernel - Re: [PATCH 0/6] powerpc/8xx: implementation of huge pages

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Message-Id: <87a8ge492u.fsf@linux.vnet.ibm.com>
Date:	Mon, 15 Aug 2016 16:01:37 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	christophe leroy <christophe.leroy@....fr>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Scott Wood <oss@...error.net>
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/6] powerpc/8xx: implementation of huge pages

christophe leroy <christophe.leroy@....fr> writes:

> Le 14/08/2016 à 16:27, Aneesh Kumar K.V a écrit :
>> Christophe Leroy <christophe.leroy@....fr> writes:
>>
>>> This set provides implementation of huge pages on the 8xx
>>>
>>> Christophe Leroy (6):
>>>   powerpc: port 64 bits pgtable_cache to 32 bits
>>>   powerpc: fix usage of _PAGE_RO in hugepage
>>>   powerpc/8xx: use r3 to scratch CR in ITLBmiss
>>>   powerpc/8xx: Move additional DTLBMiss handlers out of exception area
>>>   powerpc/8xx: make user addr DTLB miss the short path
>>>   powerpc/8xx: implementation of huge pages
>>
>> Patch 2,3,4,5 are not really related to hugepage implementation right ?
>> May be that can be sent as a separate series ?
>>
>
> Patch 2 is a lack in gup_hugepte: on 8xx, _PAGE_RW (hence _PAGE_WRITE) 
> is defined as 0 and _PAGE_RO must be set when the page in not writeable. 
> So that's a prerequisite to implementation of huge page
>
> Patch 3, 4, 5 are prerequisits for the implementation of huge page 
> handling in the TLB miss handlers:
> * 3: for huge pages implementation we need to branch base of value of 
> bit 28 and 29 of the PGD entry. For this we need to preserve CR.
> * 4: With the instructions related to hugepages, there is not enough 
> space anymore in the TLB Exception areas, so part of the it has to be 
> moved away.
> * 5: That one might be seen as not directly related to hugepages, but it 
> requires patch 3.
>
> Maybe I should reorder into 3, 4, 5, 2, 1, 6 ?
>

Can't 3,4,5,2 be merged independent of the series ? Reading then
suggested they are either fixes or performance improvements ?

-aneesh