x86/mm: factor out of top-down direct mapping setup

Create a new function memory_map_top_down to factor out of the top-down
direct memory mapping pagetable setup.  This is also a preparation for the
following patch, which will introduce the bottom-up memory mapping.  That
said, we will put the two ways of pagetable setup into separate functions,
and choose to use which way in init_mem_mapping, which makes the code more
clear.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 39 insertions, 20 deletions

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index ce32017c5e38..742d6d4ad9eb 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -418,27 +418,27 @@ static unsigned long __init get_new_step_size(unsigned long step_size)
         return step_size << 5;
 }
 
-void __init init_mem_mapping(void)
+/**
+ * memory_map_top_down - Map [map_start, map_end) top down
+ * @map_start: start address of the target memory range
+ * @map_end: end address of the target memory range
+ *
+ * This function will setup direct mapping for memory range
+ * [map_start, map_end) in top-down. That said, the page tables
+ * will be allocated at the end of the memory, and we map the
+ * memory in top-down.
+ */
+static void __init memory_map_top_down(unsigned long map_start,
+                                       unsigned long map_end)
 {
-        unsigned long end, real_end, start, last_start;
+        unsigned long real_end, start, last_start;
         unsigned long step_size;
         unsigned long addr;
         unsigned long mapped_ram_size = 0;
         unsigned long new_mapped_ram_size;
 
-        probe_page_size_mask();
-
-#ifdef CONFIG_X86_64
-        end = max_pfn << PAGE_SHIFT;
-#else
-        end = max_low_pfn << PAGE_SHIFT;
-#endif
-
-        /* the ISA range is always mapped regardless of memory holes */
-        init_memory_mapping(0, ISA_END_ADDRESS);
-
         /* xen has big range in reserved near end of ram, skip it at first.*/
-        addr = memblock_find_in_range(ISA_END_ADDRESS, end, PMD_SIZE, PMD_SIZE);
+        addr = memblock_find_in_range(map_start, map_end, PMD_SIZE, PMD_SIZE);
         real_end = addr + PMD_SIZE;
 
         /* step_size need to be small so pgt_buf from BRK could cover it */
@@ -453,13 +453,13 @@ void __init init_mem_mapping(void)
          * end of RAM in [min_pfn_mapped, max_pfn_mapped) used as new pages
          * for page table.
          */
-        while (last_start > ISA_END_ADDRESS) {
+        while (last_start > map_start) {
                 if (last_start > step_size) {
                         start = round_down(last_start - 1, step_size);
-                        if (start < ISA_END_ADDRESS)
-                                start = ISA_END_ADDRESS;
+                        if (start < map_start)
+                                start = map_start;
                 } else
-                        start = ISA_END_ADDRESS;
+                        start = map_start;
                 new_mapped_ram_size = init_range_memory_mapping(start,
                                                         last_start);
                 last_start = start;
@@ -470,8 +470,27 @@ void __init init_mem_mapping(void)
                 mapped_ram_size += new_mapped_ram_size;
         }
 
-        if (real_end < end)
-                init_range_memory_mapping(real_end, end);
+        if (real_end < map_end)
+                init_range_memory_mapping(real_end, map_end);
+}
+
+void __init init_mem_mapping(void)
+{
+        unsigned long end;
+
+        probe_page_size_mask();
+
+#ifdef CONFIG_X86_64
+        end = max_pfn << PAGE_SHIFT;
+#else
+        end = max_low_pfn << PAGE_SHIFT;
+#endif
+
+        /* the ISA range is always mapped regardless of memory holes */
+        init_memory_mapping(0, ISA_END_ADDRESS);
+
+        /* setup direct mapping for range [ISA_END_ADDRESS, end) in top-down*/
+        memory_map_top_down(ISA_END_ADDRESS, end);
 
 #ifdef CONFIG_X86_64
         if (max_pfn > max_low_pfn) {