x86, memblock: Add memblock_x86_to_bootmem()

memblock_x86_to_bootmem() will reserve memblock.reserved.region in
bootmem after bootmem is set up.

We can use it to with all arches that support memblock later.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/memblock.h

@@ -4,5 +4,6 @@
 #define ARCH_DISCARD_MEMBLOCK
 
 u64 memblock_x86_find_in_range_size(u64 start, u64 *sizep, u64 align);
+void memblock_x86_to_bootmem(u64 start, u64 end);
 
 #endif

arch/x86/mm/memblock.c

@@ -85,3 +85,32 @@ u64 __init memblock_x86_find_in_range_size(u64 start, u64 *sizep, u64 align)
 
 	return MEMBLOCK_ERROR;
 }
+
+#ifndef CONFIG_NO_BOOTMEM
+void __init memblock_x86_to_bootmem(u64 start, u64 end)
+{
+	int count;
+	u64 final_start, final_end;
+	struct memblock_region *r;
+
+	/* Take out region array itself */
+	memblock_free_reserved_regions();
+
+	count  = memblock.reserved.cnt;
+	pr_info("(%d early reservations) ==> bootmem [%010llx-%010llx]\n", count, start, end - 1);
+	for_each_memblock(reserved, r) {
+		pr_info("  [%010llx-%010llx] ", (u64)r->base, (u64)r->base + r->size - 1);
+		final_start = max(start, r->base);
+		final_end = min(end, r->base + r->size);
+		if (final_start >= final_end) {
+			pr_cont("\n");
+			continue;
+		}
+		pr_cont(" ==> [%010llx-%010llx]\n", final_start, final_end - 1);
+		reserve_bootmem_generic(final_start, final_end - final_start, BOOTMEM_DEFAULT);
+	}
+
+	/* Put region array back ? */
+	memblock_reserve_reserved_regions();
+}
+#endif