[PATCH 1/1] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.

[Jacob Shin <jacob.shin@amd.com>]

On systems with very large memory (1 TB in our case), BIOS may report a
reserved region or a hole in the E820 map, even above the 4 GB range. Exclude
these from the direct mapping.

Cc: stable@kernel.org   # > 2.6.32
Signed-off-by: Jacob Shin <jacob.shin@amd.com>
---
 arch/x86/kernel/setup.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index afaf384..af19a61 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -937,8 +937,21 @@ void __init setup_arch(char **cmdline_p)
 
 #ifdef CONFIG_X86_64
 	if (max_pfn > max_low_pfn) {
-		max_pfn_mapped = init_memory_mapping(1UL<<32,
-						     max_pfn<<PAGE_SHIFT);
+		int i;
+		for (i = 0; i < e820.nr_map; i++) {
+			struct e820entry *ei = &e820.map[i];
+
+			if (ei->addr + ei->size <= 1UL << 32)
+				continue;
+
+			if (ei->type == E820_RESERVED)
+				continue;
+
+			max_pfn_mapped = init_memory_mapping(
+				ei->addr < 1UL << 32 ? 1UL << 32 : ei->addr,
+				ei->addr + ei->size);
+		}
+
 		/* can we preseve max_low_pfn ?*/
 		max_low_pfn = max_pfn;
 	}
-- 
1.7.1