linux-kernel - Re: [PATCH 01/13] arm64: mm: Add p?d

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Message-ID: <20190218111610.GD8036@lakrids.cambridge.arm.com>
Date:   Mon, 18 Feb 2019 11:16:12 +0000
From:   Mark Rutland <Mark.Rutland@....com>
To:     Steven Price <Steven.Price@....com>
CC:     "linux-mm@...ck.org" <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" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/13] arm64: mm: Add p?d_large() definitions

On Fri, Feb 15, 2019 at 05:02:22PM +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).
>
> Expose p?d_large() from each architecture to detect these large mappings.
>
> arm64 already has these macros defined, but with a different name.
> p?d_large() is used by s390, sparc and x86. Only arm/arm64 use p?d_sect().
> Add a macro to allow both names.
>
> By not providing a pgd_large(), we get the generic version that always
> returns 0.

This last sentence isn't true until a subsequent patch, so it's probably
worth dropping it to avoid confusion.

Thanks,
Mark.

>
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>  arch/arm64/include/asm/pgtable.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index de70c1eabf33..09d308921625 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -428,6 +428,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>   PMD_TYPE_TABLE)
>  #define pmd_sect(pmd)((pmd_val(pmd) & PMD_TYPE_MASK) == \
>   PMD_TYPE_SECT)
> +#define pmd_large(x)pmd_sect(x)
>
>  #if defined(CONFIG_ARM64_64K_PAGES) || CONFIG_PGTABLE_LEVELS < 3
>  #define pud_sect(pud)(0)
> @@ -435,6 +436,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>  #else
>  #define pud_sect(pud)((pud_val(pud) & PUD_TYPE_MASK) == \
>   PUD_TYPE_SECT)
> +#define pud_large(x)pud_sect(x)
>  #define pud_table(pud)((pud_val(pud) & PUD_TYPE_MASK) == \
>   PUD_TYPE_TABLE)
>  #endif
> --
> 2.20.1
>
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