Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as memblock.memory

[Mike Rapoport]

On Mon, Feb 01, 2021 at 07:26:05PM +0800, Baoquan He wrote:
> On 02/01/21 at 10:32am, David Hildenbrand wrote:
> > 
> > 2) In init_zone_unavailable_mem(), similar to round_up(max_pfn,
> > PAGES_PER_SECTION) handling, consider range
> > 	[round_down(min_pfn, PAGES_PER_SECTION), min_pfn - 1]
> > which would handle in the x86-64 case [0..0] and, therefore, initialize PFN
> > 0.
> 
> Sounds reasonable. Maybe we can change to get the real expected lowest
> pfn from find_min_pfn_for_node() by iterating memblock.memory and
> memblock.reserved and comparing.

As I've found out the hard way [1], reserved memory is not necessary present.

There could be a system that instead of reserving memory at 0xfe000000 like
in Guillaume's report, could have it reserved at 0x0 and populated only
from the first gigabyte...
 
[1] https://lore.kernel.org/lkml/127999c4-7d56-0c36-7f88-8e1a5c934cae@xxxxxxxxxxxxx


-- 
Sincerely yours,
Mike.