[PATCH v3 04/11] arm64/mm: Add temporary arch_remove_memory() implementation

[David Hildenbrand]

A proper arch_remove_memory() implementation is on its way, which also
cleanly removes page tables in arch_add_memory() in case something goes
wrong.

As we want to use arch_remove_memory() in case something goes wrong
during memory hotplug after arch_add_memory() finished, let's add
a temporary hack that is sufficient enough until we get a proper
implementation that cleans up page table entries.

We will remove CONFIG_MEMORY_HOTREMOVE around this code in follow up
patches.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Jun Yao <yaojun8558363@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 arch/arm64/mm/mmu.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a1bfc4413982..e569a543c384 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1084,4 +1084,23 @@ int arch_add_memory(int nid, u64 start, u64 size,
 	return __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT,
 			   restrictions);
 }
+#ifdef CONFIG_MEMORY_HOTREMOVE
+void arch_remove_memory(int nid, u64 start, u64 size,
+			struct vmem_altmap *altmap)
+{
+	unsigned long start_pfn = start >> PAGE_SHIFT;
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+	struct zone *zone;
+
+	/*
+	 * FIXME: Cleanup page tables (also in arch_add_memory() in case
+	 * adding fails). Until then, this function should only be used
+	 * during memory hotplug (adding memory), not for memory
+	 * unplug. ARCH_ENABLE_MEMORY_HOTREMOVE must not be
+	 * unlocked yet.
+	 */
+	zone = page_zone(pfn_to_page(start_pfn));
+	__remove_pages(zone, start_pfn, nr_pages, altmap);
+}
+#endif
 #endif
-- 
2.20.1