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

From: Georgi Djakov
Date: Tue Sep 28 2021 - 15:34:47 EST


On 9/28/2021 9:51 PM, 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.
Without this patch, debug-related functions that use max_pfn such as
get_max_dump_pfn() or read_page_owner() will not work with any page in
memory that is hot-added after boot.

Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx>
Signed-off-by: Chris Goldsworthy <quic_cgoldswo@xxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>

Tested-by: Georgi Djakov <quic_c_gdjako@xxxxxxxxxxx>

Cc: Florian Fainelli <f.fainelli@xxxxxxxxx>
Cc: Georgi Djakov <quic_c_gdjako@xxxxxxxxxxx>
---
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)
__remove_pgd_mapping(swapper_pg_dir,
__phys_to_virt(start), size);
+ else {
+ max_pfn = PFN_UP(start + size);
+ max_low_pfn = max_pfn;
+ }
+
return ret;
}