linux-kernel - Re: [PATCH] powerpc: Use swapper_pg_dir instead of init

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Message-ID: <8dcc6a37-6b9c-45cf-bcc7-dfcc82e2da52@csgroup.eu>
Date: Sat, 16 Mar 2024 11:55:23 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] powerpc: Use swapper_pg_dir instead of init_mm->pgd



Le 09/10/2022 à 19:31, Christophe Leroy a écrit :
> init_mm->pgd is always swapper_pg_dir[] which is known
> at build time.
> 
> Directly use the later instead of loading it from init_mm
> struct at every time.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>

Dropping this patch after feedback from Michael:

no other arches do it. (swapper_pg_dir)

It would also make us the only arch other than ia64 (which is old and
probably going to get removed soon) defining pgd_offset_k().


> ---
>   arch/powerpc/include/asm/pgtable.h | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index 283f40d05a4d..f6843e6294d9 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -48,6 +48,9 @@ struct mm_struct;
>   /* Keep these as a macros to avoid include dependency mess */
>   #define pte_page(x)		pfn_to_page(pte_pfn(x))
>   #define mk_pte(page, pgprot)	pfn_pte(page_to_pfn(page), (pgprot))
> +
> +#define pgd_offset_k(address)		pgd_offset_pgd(swapper_pg_dir, (address))
> +
>   /*
>    * Select all bits except the pfn
>    */