On Thu, 18 Feb, at 03:21:25PM, Ard Biesheuvel wrote:

We treat all Boot Services regions like Loader Code/Data or free
regions: it is all recorded in memblock as usable memory, and only the
regions that are explicitly reserved are protected from further
general use.

I am currently looking into the memory attribute table, and the use
case is very similar. It would be very useful from our pov to simply
memblock_reserve() the region right after having called
efi_config_parse_tables(), and actually consume its data when we get
around to it later. The ESRT handling is already split down the middle
in the same way.

Agreed, this would also be useful in general for kexec. I've got a
couple of patches in flight that try to handle the BGRT case in a
different way,

  https://lkml.kernel.org/r/1455723910-16710-2-git-send-email-matt at codeblueprint.co.uk
  https://lkml.kernel.org/r/1455723910-16710-3-git-send-email-matt at codeblueprint.co.uk

Let me instead take a look at how we might be able to preserve only
those Boot Services regions we care out.