Subject: Re: [RFC PATCH V1 01/33] powerpc/mm: add _PAGE_HASHPTE similar to 4K hash

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 13 Jan 2016 11:32:53 +0530

Balbir Singh <[email-masked]> writes:

> On Tue, 12 Jan 2016 12:45:36 +0530
> "Aneesh Kumar K.V" <[email-masked]> wrote:
>
>> Not really needed. But this brings it back to as it was before
>> 
>
> Could you expand on not really needed. Could the changelog describe how
> the bits will be used in the follow on patches.
>

What confused me in the beginning was difference between 4k and 64k
page size. I was trying to find out whether we miss a hpte flush in any
scenario because of this. ie, a pte update on a linux pte, for which we
are doing a parallel hash pte insert. After looking at it closer my
understanding is this won't happen because pte update also look at
_PAGE_BUSY and we will wait for hash pte insert to finish before going
ahead with the pte update. But to avoid further confusion I was wondering
whether we should keep this closer to what we have with __hash_page_4k.
Hence the statement "Not really needed".

-aneesh