linux-kernel - Re: [PATCH v14 04/22] arm64: mm: Add p?d

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Message-ID: <20191030153130.GB13309@arrakis.emea.arm.com>
Date:   Wed, 30 Oct 2019 15:31:30 +0000
From:   Catalin Marinas <catalin.marinas@....com>
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>,
        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@...nel.org>, 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>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v14 04/22] arm64: mm: Add p?d_leaf() definitions

On Mon, Oct 28, 2019 at 01:58:52PM +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 will be provided by the
> p?d_leaf() functions/macros.
> 
> For arm64, we already have p?d_sect() macros which we can reuse for
> p?d_leaf().
> 
> pud_sect() is defined as a dummy function when CONFIG_PGTABLE_LEVELS < 3
> or CONFIG_ARM64_64K_PAGES is defined. However when the kernel is
> configured this way then architecturally it isn't allowed to have a
> large page at this level, and any code using these page walking macros
> is implicitly relying on the page size/number of levels being the same as
> the kernel. So it is safe to reuse this for p?d_leaf() as it is an
> architectural restriction.
> 
> CC: Catalin Marinas <catalin.marinas@....com>
> CC: Will Deacon <will@...nel.org>
> Signed-off-by: Steven Price <steven.price@....com>

I can see akpm picked these patches already. FWIW:

Acked-by: Catalin Marinas <catalin.marinas@....com>