x86: introduce max_low_pfn_mapped for 64-bit

when more than 4g memory is installed, don't map the big hole below 4g.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 20 insertions, 3 deletions

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 3451e0b3f324..9f5002e0b35c 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1056,7 +1056,7 @@ unsigned long __initdata end_user_pfn = MAX_ARCH_PFN;
 /*
  * Find the highest page frame number we have available
  */
-unsigned long __init e820_end(void)
+static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned type)
 {
         int i;
         unsigned long last_pfn = 0;
@@ -1064,12 +1064,21 @@ unsigned long __init e820_end(void)
 
         for (i = 0; i < e820.nr_map; i++) {
                 struct e820entry *ei = &e820.map[i];
+                unsigned long start_pfn;
                 unsigned long end_pfn;
 
-                if (ei->type != E820_RAM)
+                if (ei->type != type)
                         continue;
 
+                start_pfn = ei->addr >> PAGE_SHIFT;
                 end_pfn = (ei->addr + ei->size) >> PAGE_SHIFT;
+
+                if (start_pfn >= limit_pfn)
+                        continue;
+                if (end_pfn > limit_pfn) {
+                        last_pfn = limit_pfn;
+                        break;
+                }
                 if (end_pfn > last_pfn)
                         last_pfn = end_pfn;
         }
@@ -1083,7 +1092,15 @@ unsigned long __init e820_end(void)
                          last_pfn, max_arch_pfn);
         return last_pfn;
 }
+unsigned long __init e820_end_of_ram_pfn(void)
+{
+        return e820_end_pfn(MAX_ARCH_PFN, E820_RAM);
+}
 
+unsigned long __init e820_end_of_low_ram_pfn(void)
+{
+        return e820_end_pfn(1UL<<(32 - PAGE_SHIFT), E820_RAM);
+}
 /*
  * Finds an active region in the address range from start_pfn to last_pfn and
  * returns its range in ei_startpfn and ei_endpfn for the e820 entry.
@@ -1206,7 +1223,7 @@ static int __init parse_memmap_opt(char *p)
                  * the real mem size before original memory map is
                  * reset.
                  */
-                saved_max_pfn = e820_end();
+                saved_max_pfn = e820_end_of_ram_pfn();
 #endif
                 e820.nr_map = 0;
                 userdef = 1;