Subject: Re: [PATCH v3 03/11] s390x/mm: Implement arch_remove_memory()

From: Michal Hocko <[email-masked]>
Date: Mon, 1 Jul 2019 09:45:03 +0200

On Mon 27-05-19 13:11:44, David Hildenbrand wrote:
> Will come in handy when wanting to handle errors after
> arch_add_memory().

I do not understand this. Why do you add a code for something that is
not possible on this HW (based on the comment - is it still valid btw?)

> Cc: Martin Schwidefsky <[email-masked]>
> Cc: Heiko Carstens <[email-masked]>
> Cc: Andrew Morton <[email-masked]>
> Cc: Michal Hocko <[email-masked]>
> Cc: Mike Rapoport <[email-masked]>
> Cc: David Hildenbrand <[email-masked]>
> Cc: Vasily Gorbik <[email-masked]>
> Cc: Oscar Salvador <[email-masked]>
> Signed-off-by: David Hildenbrand <[email-masked]>
> ---
>  arch/s390/mm/init.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index d552e330fbcc..14955e0a9fcf 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -243,12 +243,13 @@ int arch_add_memory(int nid, u64 start, u64 size,
>  void arch_remove_memory(int nid, u64 start, u64 size,
>  			struct vmem_altmap *altmap)
>  {
> -	/*
> -	 * There is no hardware or firmware interface which could trigger a
> -	 * hot memory remove on s390. So there is nothing that needs to be
> -	 * implemented.
> -	 */
> -	BUG();
> +	unsigned long start_pfn = start >> PAGE_SHIFT;
> +	unsigned long nr_pages = size >> PAGE_SHIFT;
> +	struct zone *zone;
> +
> +	zone = page_zone(pfn_to_page(start_pfn));
> +	__remove_pages(zone, start_pfn, nr_pages, altmap);
> +	vmem_remove_mapping(start, size);
>  }
>  #endif
>  #endif /* CONFIG_MEMORY_HOTPLUG */
> -- 
> 2.20.1
> 

-- 
Michal Hocko
SUSE Labs