[PATCH 3/5] arm64: efi: avoid block mappings for unaligned UEFI memory regions

[Catalin Marinas]

On Wed, Jun 29, 2016 at 02:51:28PM +0200, Ard Biesheuvel wrote:
> +	if (!PAGE_ALIGNED(md->phys_addr) ||
> +	    !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
> +		/*
> +		 * If the end address of this region is not aligned to page
> +		 * size, the mapping is rounded up, and may end up sharing a
> +		 * page frame with the next UEFI memory region. If we create
> +		 * a block entry now, we may need to split it again when mapping
> +		 * the next region, and support for that is going to be removed
> +		 * from the MMU routines. So avoid block mappings altogether in
> +		 * that case.
> +		 */
> +		allow_block_mappings = false;
> +	}

How common is it for large areas to have unaligned start/end? I wonder
whether it's worth implementing my approach to look ahead and explicitly
check the overlap with the next section instead of disabling block
mappings altogether for this region.

-- 
Catalin