[PATCH V3 1/3] arm64/mm/hotplug: Register boot memory hot remove notifier earlier

From: Anshuman Khandual
Date: Mon Sep 21 2020 - 08:06:05 EST

This moves memory notifier registration earlier in the boot process from
device_initcall() to early_initcall() which will help in guarding against
potential early boot memory offline requests. Even though there should not
be any actual offlinig requests till memory block devices are initialized
with memory_dev_init() but then generic init sequence might just change in
future. Hence an early registration for the memory event notifier would be
helpful. While here, just skip the registration if CONFIG_MEMORY_HOTREMOVE
is not enabled and also call out when memory notifier registration fails.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Steve Capper <steve.capper@xxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
arch/arm64/mm/mmu.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 75df62fea1b6..df3b7415b128 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1499,7 +1499,17 @@ static struct notifier_block prevent_bootmem_remove_nb = {

static int __init prevent_bootmem_remove_init(void)
- return register_memory_notifier(&prevent_bootmem_remove_nb);
+ int ret = 0;
+ return ret;
+ ret = register_memory_notifier(&prevent_bootmem_remove_nb);
+ if (!ret)
+ return ret;
+ pr_err("Notifier registration failed - boot memory can be removed\n");
+ return ret;