Re: [PATCH 0/2] of: remove reserved regions count restriction

On Sun, Nov 21, 2021 at 08:43:47AM +0200, Mike Rapoport wrote:

On Fri, Nov 19, 2021 at 03:58:17PM +0800, Calvin Zhang wrote:

quoted

The count of reserved regions in /reserved-memory was limited because
the struct reserved_mem array was defined statically. This series sorts
out reserved memory code and allocates that array from early allocator.

Note: reserved region with fixed location must be reserved before any
memory allocation. While struct reserved_mem array should be allocated
after allocator is activated. We make early_init_fdt_scan_reserved_mem()
do reservation only and add another call to initialize reserved memory.
So arch code have to change for it.

I think much simpler would be to use the same constant for sizing
memblock.reserved and reserved_mem arrays.

If there is too much reserved regions in the device tree, reserving them in
memblock will fail anyway because memblock also starts with static array
for memblock.reserved, so doing one pass with memblock_reserve() and
another to set up reserved_mem wouldn't help anyway.

Yes. This happens only if there are two many fixed reserved regions.
memblock.reserved can be resized after paging.

I also find another problem. Initializing dynamic reservation after
paging would fail to mark it no-map because no-map flag works when doing
direct mapping. This seems to be a circular dependency.

Thank You,
Calvin