arm64: Add memory hotplug support

Wire up the basic support for hot-adding memory. Since memory hotplug
is fairly tightly coupled to sparsemem, we tweak pfn_valid() to also
cross-check the presence of a section in the manner of the generic
implementation, before falling back to memblock to check for no-map
regions within a present section as before. By having arch_add_memory(()
create the linear mapping first, this then makes everything work in the
way that __add_section() expects.

We expect hotplug to be ACPI-driven, so the swapper_pg_dir updates
should be safe from races by virtue of the global device hotplug lock.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index 27a31efd9e8e..ae34e3a1cef1 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c
@@ -466,3 +466,13 @@ void __init arm64_numa_init(void)
 
 	numa_init(dummy_numa_init);
 }
+
+/*
+ * We hope that we will be hotplugging memory on nodes we already know about,
+ * such that acpi_get_node() succeeds and we never fall back to this...
+ */
+int memory_add_physaddr_to_nid(u64 addr)
+{
+	pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
+	return 0;
+}