I wrote a patch to avoid redundant memory hot-add call at boot time. This
was cause of strange fail message of memory hotplug like "ACPI: add_memory
failed". Memory is recognized by early boot code with EFI/E820.
But, if DSDT describes memory devices for them, then hot-add code is called
for already recognized memory, and it shows fail messages with -EEXIST.
So, sys admin will misunderstand this message as something wrong by it.
This patch avoids them by preventing redundant hot-add call until
completion of driver initialization.