linux-kernel - Re: [PATCH v17 15/15] arm64: trans_pgd: remove trans_pgd_map

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Message-ID: <YVSXtswhm6iTC3yz@arm.com>
Date:   Wed, 29 Sep 2021 17:43:34 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     jmorris@...ei.org, sashal@...nel.org, ebiederm@...ssion.com,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        corbet@....net, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, maz@...nel.org,
        james.morse@....com, vladimir.murzin@....com,
        matthias.bgg@...il.com, linux-mm@...ck.org, mark.rutland@....com,
        steve.capper@....com, rfontana@...hat.com, tglx@...utronix.de,
        selindag@...il.com, tyhicks@...ux.microsoft.com,
        kernelfans@...il.com, akpm@...ux-foundation.org,
        madvenka@...ux.microsoft.com
Subject: Re: [PATCH v17 15/15] arm64: trans_pgd: remove trans_pgd_map_page()

On Thu, Sep 16, 2021 at 07:13:25PM -0400, Pasha Tatashin wrote:
> The intend of trans_pgd_map_page() was to map contiguous range of VA
> memory to the memory that is getting relocated during kexec. However,
> since we are now using linear map instead of contiguous range this
> function is not needed
> 
> Suggested-by: Pingfan Liu <kernelfans@...il.com>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> ---
>  arch/arm64/include/asm/trans_pgd.h |  5 +--
>  arch/arm64/mm/trans_pgd.c          | 57 ------------------------------
>  2 files changed, 1 insertion(+), 61 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/trans_pgd.h b/arch/arm64/include/asm/trans_pgd.h
> index 7b04d32b102c..033d400a4ea4 100644
> --- a/arch/arm64/include/asm/trans_pgd.h
> +++ b/arch/arm64/include/asm/trans_pgd.h
> @@ -15,7 +15,7 @@
>  /*
>   * trans_alloc_page
>   *	- Allocator that should return exactly one zeroed page, if this
> - *	  allocator fails, trans_pgd_create_copy() and trans_pgd_map_page()
> + *	  allocator fails, trans_pgd_create_copy() and trans_pgd_idmap_page()
>   *	  return -ENOMEM error.
>   *
>   * trans_alloc_arg
> @@ -30,9 +30,6 @@ struct trans_pgd_info {
>  int trans_pgd_create_copy(struct trans_pgd_info *info, pgd_t **trans_pgd,
>  			  unsigned long start, unsigned long end);
>  
> -int trans_pgd_map_page(struct trans_pgd_info *info, pgd_t *trans_pgd,
> -		       void *page, unsigned long dst_addr, pgprot_t pgprot);

So this function never got used in mainline after commit 7018d467ff2d
("arm64: trans_pgd: hibernate: idmap the single page that holds the copy
page routines"). I guess it's because we merged part of v10 of this
series and in v12 you dropped the contiguous VA range in favour of a
copy of the linear map.

-- 
Catalin