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Subject: Re: [PATCH 06/13] mm: pagewalk: Add 'depth' parameter to pte_hole
From:   William Kucharski <william.kucharski@oracle.com>
In-Reply-To: <20190215170235.23360-7-steven.price@arm.com>
Date:   Wed, 20 Feb 2019 04:35:11 -0700
Cc:     Linux-MM <linux-mm@kvack.org>, Andy Lutomirski <luto@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        James Morse <james.morse@arm.com>,
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        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will.deacon@arm.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
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 <20190215170235.23360-7-steven.price@arm.com>
To:     Steven Price <Steven.Price@arm.com>
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> On Feb 15, 2019, at 10:02 AM, Steven Price <Steven.Price@arm.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?

Thanks!