[PATCH v5sub1 8/8] arm64: allow kernel Image to be loaded anywhere in physical memory

On 1 February 2016 at 16:06, Catalin Marinas [off-list ref] wrote:

On Mon, Feb 01, 2016 at 11:54:53AM +0100, Ard Biesheuvel wrote:

quoted

Note that limiting memory using mem= is not unambiguous anymore after
this change, considering that the kernel may be at the top of physical
memory, and clipping from the bottom rather than the top will discard
any 32-bit DMA addressable memory first. To deal with this, the handling
of mem= is reimplemented to clip top down, but take special care not to
clip memory that covers the kernel image.

I may have forgotten the reason - why do we need to avoid clipping the
memory that covers the kernel image? It's already mapped in the vmalloc
area, so we wouldn't need it in the linear map as well.

Good question. Originally, I needed it for swapper_pg_dir, whose
pud/pmd/pte levels were accessed via __va() translations of the values
found in the higher-up table entries, but after Mark's patches, only
the top level pgd of swapper_pg_dir is still used. Similarly, for
idmap_pg_dir, we don't change any mappings at runtime so the same
applies there I think.

I will try dropping this, and see what happens.

-- 
Ard.