linux-kernel - Re: [PATCH 06/13] mm: pagewalk: Add 'depth' parameter to pte

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Message-ID: <76ce9f9b-eb0d-6ad5-9f57-ff3a8fa6b074@arm.com>
Date:   Wed, 20 Feb 2019 14:10:45 +0000
From:   Steven Price <steven.price@....com>
To:     William Kucharski <william.kucharski@...cle.com>
Cc:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        James Morse <james.morse@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 06/13] mm: pagewalk: Add 'depth' parameter to pte_hole

On 20/02/2019 11:35, William Kucharski wrote:
> 
> 
>> On Feb 15, 2019, at 10:02 AM, Steven Price <Steven.Price@....com> wrote:
>>
>> The pte_hole() callback is called at multiple levels of the page tables.
>> Code dumping the kernel page tables needs to know what at what depth
>> the missing entry is. Add this is an extra parameter to pte_hole().
>> When the depth isn't know (e.g. processing a vma) then -1 is passed.
>>
>> Note that depth starts at 0 for a PGD so that PUD/PMD/PTE retain their
>> natural numbers as levels 2/3/4.
> 
> Nit: Could you add a comment noting this for anyone wondering how to
> calculate the level numbers in the future?

Good point! I'll expand the comment in the header file.

Thanks,

Steve