linux-kernel - Re: [PATCH v13 06/14] mm: HUGE

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Message-ID: <303a93df-6b32-1b3e-d293-b569e1a4b03e@csgroup.eu>
Date:   Wed, 28 Apr 2021 10:32:58 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Nicholas Piggin <npiggin@...il.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Christoph Hellwig <hch@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ding Tianhong <dingtianhong@...wei.com>,
        linuxppc-dev@...ts.ozlabs.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v13 06/14] mm: HUGE_VMAP arch support cleanup



Le 17/03/2021 à 07:23, Nicholas Piggin a écrit :
> This changes the awkward approach where architectures provide init
> functions to determine which levels they can provide large mappings for,
> to one where the arch is queried for each call.
> 
> This removes code and indirection, and allows constant-folding of dead
> code for unsupported levels.
> 
> This also adds a prot argument to the arch query. This is unused
> currently but could help with some architectures (e.g., some powerpc
> processors can't map uncacheable memory with large pages).
> 
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: x86@...nel.org
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Reviewed-by: Ding Tianhong <dingtianhong@...wei.com>
> Acked-by: Catalin Marinas <catalin.marinas@....com> [arm64]
> Signed-off-by: Nicholas Piggin <npiggin@...il.com>
> ---
>   arch/arm64/include/asm/vmalloc.h         |  8 ++
>   arch/arm64/mm/mmu.c                      | 10 +--
>   arch/powerpc/include/asm/vmalloc.h       |  8 ++
>   arch/powerpc/mm/book3s64/radix_pgtable.c |  8 +-
>   arch/x86/include/asm/vmalloc.h           |  7 ++
>   arch/x86/mm/ioremap.c                    | 12 +--
>   include/linux/io.h                       |  9 ---
>   include/linux/vmalloc.h                  |  6 ++
>   init/main.c                              |  1 -
>   mm/debug_vm_pgtable.c                    |  4 +-
>   mm/ioremap.c                             | 94 ++++++++++--------------
>   11 files changed, 87 insertions(+), 80 deletions(-)
> 

> diff --git a/mm/ioremap.c b/mm/ioremap.c
> index 3f4d36f9745a..3264d0203785 100644
> --- a/mm/ioremap.c
> +++ b/mm/ioremap.c
> @@ -16,49 +16,16 @@
>   #include "pgalloc-track.h"
>   
>   #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
> -static int __read_mostly ioremap_p4d_capable;
> -static int __read_mostly ioremap_pud_capable;
> -static int __read_mostly ioremap_pmd_capable;
> -static int __read_mostly ioremap_huge_disabled;
> +static bool __ro_after_init iomap_max_page_shift = PAGE_SHIFT;

Must be an int, not a bool.

>   
>   static int __init set_nohugeiomap(char *str)
>   {
> -	ioremap_huge_disabled = 1;
> +	iomap_max_page_shift = P4D_SHIFT;
>   	return 0;
>   }
>   early_param("nohugeiomap", set_nohugeiomap);
> -
> -void __init ioremap_huge_init(void)
> -{
> -	if (!ioremap_huge_disabled) {
> -		if (arch_ioremap_p4d_supported())
> -			ioremap_p4d_capable = 1;
> -		if (arch_ioremap_pud_supported())
> -			ioremap_pud_capable = 1;
> -		if (arch_ioremap_pmd_supported())
> -			ioremap_pmd_capable = 1;
> -	}
> -}
> -
> -static inline int ioremap_p4d_enabled(void)
> -{
> -	return ioremap_p4d_capable;
> -}
> -
> -static inline int ioremap_pud_enabled(void)
> -{
> -	return ioremap_pud_capable;
> -}
> -
> -static inline int ioremap_pmd_enabled(void)
> -{
> -	return ioremap_pmd_capable;
> -}
> -
> -#else	/* !CONFIG_HAVE_ARCH_HUGE_VMAP */
> -static inline int ioremap_p4d_enabled(void) { return 0; }
> -static inline int ioremap_pud_enabled(void) { return 0; }
> -static inline int ioremap_pmd_enabled(void) { return 0; }
> +#else /* CONFIG_HAVE_ARCH_HUGE_VMAP */
> +static const bool iomap_max_page_shift = PAGE_SHIFT;
>   #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
>   
>   static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,

Christophe