linux-kernel - Re: [PATCH v2 03/13] mm: Add generic p?d

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Message-ID: <20190221142812.oa53lfnnfmsuh6ys@kshutemo-mobl1>
Date:   Thu, 21 Feb 2019 17:28:12 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Steven Price <steven.price@....com>
Cc:     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>
Subject: Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros

On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> From: James Morse <james.morse@....com>
> 
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
> 
> For architectures that don't provide p?d_large() macros, provided a
> does nothing default.

Nak, sorry.

Power will get broken by the patch. It has pmd_large() inline function,
that will be overwritten by the define from this patch.

I believe it requires more ground work on arch side in general.
All architectures that has huge page support has to provide these helpers
(and matching defines) before you can use it in a generic code.

-- 
 Kirill A. Shutemov