linux-kernel - Re: [PATCH v3 05/34] c6x: mm: Add p?d

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Message-ID: <f840db0e-bbb3-db7e-d883-79b5a630767c@arm.com>
Date:   Mon, 4 Mar 2019 12:01:37 +0000
From:   Steven Price <steven.price@....com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Mark Rutland <Mark.Rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will.deacon@....com>, linux-mm@...ck.org,
        "H. Peter Anvin" <hpa@...or.com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        linux-c6x-dev@...ux-c6x.org, x86@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        Mark Salter <msalter@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Aurelien Jacquiot <jacquiot.aurelien@...il.com>,
        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,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, James Morse <james.morse@....com>
Subject: Re: [PATCH v3 05/34] c6x: mm: Add p?d_large() definitions

On 01/03/2019 21:48, Kirill A. Shutemov wrote:
> On Wed, Feb 27, 2019 at 05:05:39PM +0000, 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_large() functions/macros.
>>
>> For c6x there's no MMU so there's never a large page, so just add stubs.
> 
> Other option would be to provide the stubs via generic headers form !MMU.
> 

I agree that could be done, but equally the definitions of
p?d_present/p?d_none/p?d_bad etc could be provided by a generic header
for !MMU but currently are not. It makes sense to keep the p?d_large
definitions next to the others.

I'd prefer to stick with a (relatively) small change here - it's already
quite a long series! But this is certainly something that could be
tidied up for !MMU archs.

Steve