[PATCH v2 5/9] arm64: mm: move vmemmap region right below the linear region

[Catalin Marinas]

On Mon, Feb 29, 2016 at 03:44:40PM +0100, Ard Biesheuvel wrote:
> @@ -404,6 +404,12 @@ void __init mem_init(void)
>  	BUILD_BUG_ON(TASK_SIZE_32			> TASK_SIZE_64);
>  #endif
>  
> +	/*
> +	 * Make sure we chose the upper bound of sizeof(struct page)
> +	 * correctly.
> +	 */
> +	BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));

Since with the vmemmap fix you already assume that PAGE_OFFSET is half
of the VA space, we should add another check on PAGE_OFFSET !=
UL(0xffffffffffffffff) << (VA_BITS - 1), just in case someone thinks
they could map a bit of extra RAM without going for a larger VA.

-- 
Catalin