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

[Will Deacon]

On Tue, Mar 08, 2016 at 09:09:29PM +0700, 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 <mlangsdo at redhat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
>  arch/arm64/include/asm/pgtable.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Sorry for the slight delay, I was flying back from the US and didn't
read mail for a couple of days. Anyway, I'll send this for 4.5 along
with a CC stable and the various tested-bys. Hopefully it won't be too
late for final.

Will