linux-kernel - Re: [PATCH] arm64/mm: Drop use_1G

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Message-ID: <fbf2d9f5-2226-dbd8-af3b-096fa2020381@arm.com>
Date:   Wed, 16 Feb 2022 10:44:54 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/mm: Drop use_1G_block()



On 2/16/22 10:36 AM, Anshuman Khandual wrote:
> pud_sect_supported() already checks for PUD level block mapping support i.e
> on ARM64_4K_PAGES config. Hence pud_sect_supported(), along with some other
> required alignment checks can help completely drop use_1G_block().
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This applies on v5.17-rc4
> 
>  arch/arm64/mm/mmu.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index acfae9b41cc8..5a7954c9e6ec 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -294,18 +294,6 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr,
>  	} while (addr = next, addr != end);
>  }
>  
> -static inline bool use_1G_block(unsigned long addr, unsigned long next,
> -			unsigned long phys)
> -{
> -	if (PAGE_SHIFT != 12)
> -		return false;
> -
> -	if (((addr | next | phys) & ~PUD_MASK) != 0)
> -		return false;
> -
> -	return true;
> -}
> -
>  static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
>  			   phys_addr_t phys, pgprot_t prot,
>  			   phys_addr_t (*pgtable_alloc)(int),
> @@ -338,7 +326,8 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
>  		/*
>  		 * For 4K granule only, attempt to put down a 1GB block
>  		 */
> -		if (use_1G_block(addr, next, phys) &&
> +		if (pud_sect_supported() &&
> +		   ((addr | next | phys) & ~PUD_MASK) == 0 &&
>  		    (flags & NO_BLOCK_MAPPINGS) == 0) {

This is now very similar to init_pmd() block mapping check.

>  			pud_set_huge(pudp, phys, prot);
>  
>