efi: Tag memblock reservations of boot services regions as RSRV_KERN

By definition, EFI memory regions of type boot services code or data
have no special significance to the firmware at runtime, only to the OS.
In some cases, the firmware will allocate tables and other assets that
are passed in memory in regions of this type, and leave it up to the OS
to decide whether or not to treat the allocation as special, or simply
consume the contents at boot and recycle the RAM for ordinary use. The
reason for this approach is that it avoids needless memory reservations
for assets that the OS knows nothing about, and therefore doesn't know
how to free either.

This means that any memblock reservations covering such regions can be
marked as MEMBLOCK_RSRV_KERN - this is a better match semantically, and
is useful on x86 to distinguish true reservations from temporary
reservations that are only needed to work around firmware bugs.

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: ardbiesheuvel

drivers/firmware/efi/efi.c

@@ -600,7 +600,9 @@ void __init efi_mem_reserve(phys_addr_t addr, u64 size)
 		return;
 
 	if (!memblock_is_region_reserved(addr, size))
-		memblock_reserve(addr, size);
+		memblock_reserve_kern(addr, size);
+	else
+		memblock_reserved_mark_kern(addr, size);
 
 	/*
 	 * Some architectures (x86) reserve all boot services ranges