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, 7 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/amd_64.c b/arch/x86/kernel/cpu/amd_64.c
index 958526d6a74..bd182b7616e 100644
--- a/arch/x86/kernel/cpu/amd_64.c
+++ b/arch/x86/kernel/cpu/amd_64.c
@@ -199,10 +199,14 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
                  * Don't do it for gbpages because there seems very little
                  * benefit in doing so.
                  */
-                if (!rdmsrl_safe(MSR_K8_TSEG_ADDR, &tseg) &&
-                    (tseg >> PMD_SHIFT) <
-                        (max_pfn_mapped >> (PMD_SHIFT-PAGE_SHIFT)))
+                if (!rdmsrl_safe(MSR_K8_TSEG_ADDR, &tseg)) {
+                    if ((tseg>>PMD_SHIFT) <
+                                (max_low_pfn_mapped>>(PMD_SHIFT-PAGE_SHIFT)) ||
+                        ((tseg>>PMD_SHIFT) <
+                                (max_pfn_mapped>>(PMD_SHIFT-PAGE_SHIFT)) &&
+                         (tseg>>PMD_SHIFT) >= (1ULL<<(32 - PMD_SHIFT))))
                         set_memory_4k((unsigned long)__va(tseg), 1);
+                }
         }
 }