Re: [PATCH v3 1/2] x86/setup: don't remove E820_TYPE_RAM for pfn 0

Mike Rapoport
2021-01-13T11:24:30Z

On Wed, Jan 13, 2021 at 09:56:49AM +0100, Oscar Salvador wrote:
> On Mon, Jan 11, 2021 at 09:40:16PM +0200, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@linux.ibm.com>
> >
> > The first 4Kb of memory is a BIOS owned area and to avoid its allocation
> > for the kernel it was not listed in e820 tables as memory. As the result,
> > pfn 0 was never recognised by the generic memory management and it is not a
> > part of neither node 0 nor ZONE_DMA.
>
> So, since it never was added to memblock.memory structs, it was not
> initialized by init_unavailable_mem, right?

Actually it was initialized by init_unavailable_mem() and got zone=0 and
node=0, but the DMA zone started from pfn 1, so pfn 0 was never a part of
ZONE_DMA.

> --
> Oscar Salvador
> SUSE L3

--
Sincerely yours,
Mike.