Subject: [PATCH] arm64: account for sparsemem section alignment when choosing vmemmap offset

From: [email-masked] (David Daney)
Date: Tue, 08 Mar 2016 12:08:04 -0800

On 03/08/2016 06:09 AM, Ard Biesheuvel wrote:
> Commit dfd55ad85e4a ("arm64: vmemmap: use virtual projection of linear
> region") fixed an issue where the struct page array would overflow into the
> adjacent virtual memory region if system RAM was placed so high up in
> physical memory that its addresses were not representable in the build time
> configured virtual address size.
>
> However, the fix failed to take into account that the vmemmap region needs
> to be relatively aligned with respect to the sparsemem section size, so that
> a sequence of page structs corresponding with a sparsemem section in the
> linear region appears naturally aligned in the vmemmap region.
>
> So round up vmemmap to sparsemem section size. Since this essentially moves
> the projection of the linear region up in memory, also revert the reduction
> of the size of the vmemmap region.
>
> Fixes: dfd55ad85e4a ("arm64: vmemmap: use virtual projection of linear region")
> Tested-by: Mark Langsdorf <[email-masked]>

For me, this fixes the failures caused by dfd55ad85e4a

Tested-by: David Daney <[email-masked]>

> Signed-off-by: Ard Biesheuvel <[email-masked]>
> ---
>   arch/arm64/include/asm/pgtable.h | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index f50608674580..819aff5d593f 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -40,7 +40,7 @@
>    * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space,
>    *	fixed mappings and modules
>    */
> -#define VMEMMAP_SIZE		ALIGN((1UL << (VA_BITS - PAGE_SHIFT - 1)) * sizeof(struct page), PUD_SIZE)
> +#define VMEMMAP_SIZE		ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)
>
>   #ifndef CONFIG_KASAN
>   #define VMALLOC_START		(VA_START)
> @@ -52,7 +52,8 @@
>   #define VMALLOC_END		(PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)
>
>   #define VMEMMAP_START		(VMALLOC_END + SZ_64K)
> -#define vmemmap			((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
> +#define vmemmap			((struct page *)VMEMMAP_START - \
> +				 SECTION_ALIGN_DOWN(memstart_addr >> PAGE_SHIFT))
>
>   #define FIRST_USER_ADDRESS	0UL
>
>