arm64: mm: update max_pfn after memory hotplug

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: 4ab2150 ("arm64: Add memory hotplug support")
Signed-off-by: Sudarshan Rajagopalan <[email protected]>
Signed-off-by: Chris Goldsworthy <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Florian Fainelli <[email protected]>
Cc: Georgi Djakov <[email protected]>
Tested-by: Georgi Djakov <[email protected]>
Link: https://lore.kernel.org/r/a51a27ee7be66024b5ce626310d673f24107bcb8.1632853776.git.quic_cgoldswo@quicinc.com
Signed-off-by: Will Deacon <[email protected]>

Author: Sudarshan Rajagopalan

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;
 }