linux-kernel - Re: [RFC PATCH 2/2] ARM: memory-failure: not select RAS and MEMORY

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Message-ID: <91041fd5-ca37-4a6f-981c-74aa92bb2291@redhat.com>
Date: Mon, 22 Sep 2025 10:15:09 +0200
From: David Hildenbrand <david@...hat.com>
To: Xie Yuanbin <xieyuanbin1@...wei.com>, linux@...linux.org.uk,
 akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com,
 mhocko@...e.com, linmiaohe@...wei.com, nao.horiguchi@...il.com,
 rmk+kernel@...linux.org.uk, ardb@...nel.org, nathan@...nel.org,
 ebiggers@...nel.org, arnd@...db.de, rostedt@...dmis.org, kees@...nel.org,
 dave@...ilevsky.ca, peterz@...radead.org, Minchan Kim <minchan@...nel.org>
Cc: will@...nel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org, liaohua4@...wei.com,
 lilinjie8@...wei.com
Subject: Re: [RFC PATCH 2/2] ARM: memory-failure: not select RAS and
 MEMORY_ISOLATION

On 22.09.25 04:14, Xie Yuanbin wrote:
> For memory-failure on ARM, these features do not seem necessary.
> 
> Signed-off-by: Xie Yuanbin <xieyuanbin1@...wei.com>
> ---
>   mm/Kconfig          | 4 ++--
>   mm/memory-failure.c | 2 ++
>   2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 034a1662d8c1..22eefc4747d5 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -742,22 +742,22 @@ config DEFAULT_MMAP_MIN_ADDR
>   	  This value can be changed after boot using the
>   	  /proc/sys/vm/mmap_min_addr tunable.
>   
>   config ARCH_SUPPORTS_MEMORY_FAILURE
>   	bool
>   
>   config MEMORY_FAILURE
>   	depends on MMU
>   	depends on ARCH_SUPPORTS_MEMORY_FAILURE
>   	bool "Enable recovery from hardware memory errors"
> -	select MEMORY_ISOLATION
> -	select RAS
> +	select MEMORY_ISOLATION if !ARM
> +	select RAS if !ARM

I'm trying to figure out why we need MEMORY_ISOLATION at all.

MEMORY_ISOLATION is mostly required for memory offlining and 
alloc_contig_range()/cma -- it controls the availability of the 
"isolate" bit in the pageblock.

What CONFIG_MEMORY_FAILURE soft-offline support wants is migrate_pages() 
support. But that comes with CONFIG_MIGRATION.

And isolate_folio_to_list() has nothing to do with CONFIG_MEMORY_ISOLATION.

We added that "select MEMORY_ISOLATION" in commit ee6f509c3274 ("mm: 
factor out memory isolate functions").

Turns out we remove the need for that in add05cecef80 ("mm: 
soft-offline: don't free target page in successful page migration") 
where we removed the calls to set_migratetype_isolate() etc.

Can you send a patch to remove the "select MEMORY_ISOLATION" independent 
of any arm changes?

-- 
Cheers

David / dhildenb