Re: [PATCH v4 3/6] mm/hotplug: Allow architecture to override memmap on memory support check

[David Hildenbrand <david@redhat.com>]

On 18.07.23 04:44, Aneesh Kumar K.V wrote:
> Some architectures would want different restrictions. Hence add an
> architecture-specific override.
> 
> Both the PMD_SIZE check and pageblock alignment check are moved there.

No :)

> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>   mm/memory_hotplug.c | 22 +++++++++++++++++++---
>   1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 1b19462f4e72..5921c81fcb70 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1247,9 +1247,25 @@ static int online_memory_block(struct memory_block *mem, void *arg)
>   	return device_online(&mem->dev);
>   }
>   
> +#ifndef arch_supports_memmap_on_memory
> +static inline bool arch_supports_memmap_on_memory(unsigned long size)
> +{
> +	unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
> +	unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
> +
> +	/*
> +	 * As default, we want the vmemmap to span a complete PMD such that we
> +	 * can map the vmemmap using a single PMD if supported by the
> +	 * architecture.
> +	 */
> +	return IS_ALIGNED(vmemmap_size, PMD_SIZE);
> +}
> +#endif
> +
>   static bool mhp_supports_memmap_on_memory(unsigned long size)
>   {
> -	unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
> +
> +	unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
>   	unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
>   	unsigned long remaining_size = size - vmemmap_size;
>   
> @@ -1281,8 +1297,8 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
>   	 */
>   	return mhp_memmap_on_memory() &&
>   	       size == memory_block_size_bytes() &&
> -	       IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> -	       IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
> +	       IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT)) &&
> +	       arch_supports_memmap_on_memory(size);
>   }
>   
>   /*

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb