[PATCH 5/7] RISC-V: Implement memory hotplug

[Logan Gunthorpe <logang@deltatee.com>]

In order to define ARCH_ENABLE_MEMORY_HOTPLUG we need to implement
arch_add_memory() and vmemmap_free().

arch_add_memory() is very similar to the x86 versions except we
don't need to fuss with the mapping as we've already mapped the
entire linear region in riscv.

For now, vmemmap_free() is empty which is similar to other arches that
don't implement hot remove.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Anup Patel <anup.patel@wdc.com>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Zong Li <zong@andestech.com>
Cc: Guo Ren <ren_guo@c-sky.com>
---
 arch/riscv/Kconfig   |  3 +++
 arch/riscv/mm/init.c | 27 +++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index d21e6a12e8b6..9477214a00e7 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -83,6 +83,9 @@ config ARCH_SPARSEMEM_ENABLE
 config ARCH_SELECT_MEMORY_MODEL
 	def_bool ARCH_SPARSEMEM_ENABLE
 
+config ARCH_ENABLE_MEMORY_HOTPLUG
+	def_bool y
+
 config STACKTRACE_SUPPORT
 	def_bool y
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 315194557c3d..0a54c3adf0ac 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -238,3 +238,30 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 	return vmemmap_populate_basepages(start, end, node);
 }
 #endif
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+void vmemmap_free(unsigned long start, unsigned long end,
+		  struct vmem_altmap *altmap)
+{
+}
+
+int arch_add_memory(int nid, u64 start, u64 size, struct vmem_altmap *altmap,
+		    bool want_memblock)
+{
+	unsigned long start_pfn = start >> PAGE_SHIFT;
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+	int ret;
+
+	if ((start + size) > -va_pa_offset) {
+		pr_err("Cannot hotplug memory from %08llx to %08llx as it doesn't fall within the linear mapping\n",
+		       start, start + size);
+		return -EFAULT;
+	}
+
+	ret = __add_pages(nid, start_pfn, nr_pages, altmap, want_memblock);
+	WARN_ON_ONCE(ret);
+
+	return ret;
+}
+
+#endif
-- 
2.20.1