linux-kernel - Re: [PATCH v3 15/34] parisc: mm: Add p?d

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Date:   Tue, 5 Mar 2019 22:45:55 +0100
From:   Helge Deller <deller@....de>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Steven Price <steven.price@....com>, linux-mm@...ck.org,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        linux-parisc@...r.kernel.org
Subject: Re: [PATCH v3 15/34] parisc: mm: Add p?d_large() definitions

On 01.03.19 23:12, Kirill A. Shutemov wrote:
> On Wed, Feb 27, 2019 at 07:54:22PM +0100, Helge Deller wrote:
>> On 27.02.19 18:05, 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 parisc, we don't support large pages, so add stubs returning 0.
>>
>> We do support huge pages on parisc, but not yet on those levels.
> 
> Just curious, what level do parisc supports huge pages on?
> AFAICS, it can have 2- or 3- level paging and the patch defines helpers
> for two level: pgd and pmd. Hm?

You are correct.
My comment was misleading and meant to say that we do support generic
huge pages for applications.

Helge