linux-kernel - Re: [RFC V2 10/10] arm64/mm: Enable CONFIG_ARM64_PA_BITS_52 on CONFIG_ARM64_[4K|16K]

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Date:   Thu, 5 Aug 2021 18:23:15 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        suzuki.poulose@....com, mark.rutland@....com, will@...nel.org,
        maz@...nel.org, james.morse@....com, steven.price@....com
Subject: Re: [RFC V2 10/10] arm64/mm: Enable CONFIG_ARM64_PA_BITS_52 on
 CONFIG_ARM64_[4K|16K]_PAGES

On Mon, Jul 26, 2021 at 12:07:25PM +0530, Anshuman Khandual wrote:
> All required FEAT_LPA2 components for 52 bit PA range are already in place.
> Just enable CONFIG_ARM64_PA_BITS_52 on 4K and 16K pages which would select
> CONFIG_ARM64_PA_BITS_52_LPA2 activating 52 bit PA range via FEAT_LPA2.
> 
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>  arch/arm64/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1999ac6..ce139415 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -952,9 +952,9 @@ config ARM64_PA_BITS_48
>  
>  config ARM64_PA_BITS_52
>  	bool "52-bit (ARMv8.2)"
> -	depends on ARM64_64K_PAGES
>  	depends on ARM64_PAN || !ARM64_SW_TTBR0_PAN
>  	select ARM64_PA_BITS_52_LPA if ARM64_64K_PAGES
> +	select ARM64_PA_BITS_52_LPA2 if (ARM64_4K_PAGES  || ARM64_16K_PAGES)
>  	help
>  	  Enable support for a 52-bit physical address space, introduced as
>  	  part of the ARMv8.2-LPA extension.

If you do it this way, the text here needs updating and the 8.2
architecture version removed.

-- 
Catalin