linux-kernel - [PATCH 168/270] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.

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Date:	Mon, 26 Nov 2012 14:57:38 -0200
From:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jacob Shin <jacob.shin@....com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Subject: [PATCH 168/270] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.

3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jacob Shin <jacob.shin@....com>

commit 1bbbbe779aabe1f0768c2bf8f8c0a5583679b54a upstream.

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.

[ hpa: this should be done not just for > 4 GB but for everything above the legacy
  region (1 MB), at the very least.  That, however, turns out to require significant
  restructuring.  That work is well underway, but is not suitable for rc/stable. ]

Signed-off-by: Jacob Shin <jacob.shin@....com>
Link: http://lkml.kernel.org/r/1319145326-13902-1-git-send-email-jacob.shin@amd.com
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
---
 arch/x86/kernel/setup.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 16be6dc..e615c31 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -919,8 +919,21 @@ 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;
 	}
-- 
1.7.9.5

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