Re: [RFC] arm64: mm: update max_pfn after memory hotplug

From: Georgi Djakov
Date: Mon Sep 27 2021 - 13:28:02 EST

On 9/24/2021 1:54 AM, Chris Goldsworthy wrote:
From: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx>

After new memory blocks have been hotplugged, max_pfn and max_low_pfn
needs updating to reflect on new PFNs being hot added to system.

Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx>
Signed-off-by: Chris Goldsworthy <quic_cgoldswo@xxxxxxxxxxx>

Thanks for the patch, Chris!

With this patch, the data in /proc/kpageflags appears to be correct and
memory tools like procrank work again on arm64 platforms.

Tested-by: Georgi Djakov <quic_c_gdjako@xxxxxxxxxxx>

Maybe we should add fixes tag, as it has been broken since the following
Fixes: abec749facff ("fs/proc/page.c: allow inspection of last section and fix end detection")


arch/arm64/mm/mmu.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index cfd9deb..fd85b51 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
if (ret)
__phys_to_virt(start), size);
+ else {
+ max_pfn = PFN_UP(start + size);
+ max_low_pfn = max_pfn;
+ }
return ret;