linux-kernel - Re: [PATCH v3 02/11] s390x/mm: Fail when an altmap is used for arch_add

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Date:   Mon, 1 Jul 2019 09:43:06 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-ia64@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, akpm@...ux-foundation.org,
        Dan Williams <dan.j.williams@...el.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Oscar Salvador <osalvador@...e.com>
Subject: Re: [PATCH v3 02/11] s390x/mm: Fail when an altmap is used for
 arch_add_memory()

On Mon 27-05-19 13:11:43, David Hildenbrand wrote:
> ZONE_DEVICE is not yet supported, fail if an altmap is passed, so we
> don't forget arch_add_memory()/arch_remove_memory() when unlocking
> support.

Why do we need this? Sure ZONE_DEVICE is not supported for s390 and so
might be the case for other arches which support hotplug. I do not see
much point in adding warning to each of them.

> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Oscar Salvador <osalvador@...e.com>
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/s390/mm/init.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 14d1eae9fe43..d552e330fbcc 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -226,6 +226,9 @@ int arch_add_memory(int nid, u64 start, u64 size,
>  	unsigned long size_pages = PFN_DOWN(size);
>  	int rc;
>  
> +	if (WARN_ON_ONCE(restrictions->altmap))
> +		return -EINVAL;
> +
>  	rc = vmem_add_mapping(start, size);
>  	if (rc)
>  		return rc;
> -- 
> 2.20.1
> 

-- 
Michal Hocko
SUSE Labs