linux-kernel - [PATCH 4.2 031/134] arm64: set MAX_MEMBLOCK

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Date:	Sat, 26 Sep 2015 13:54:43 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
	Stuart Yoder <stuart.yoder@...escale.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Will Deacon <will.deacon@....com>
Subject: [PATCH 4.2 031/134] arm64: set MAX_MEMBLOCK_ADDR according to linear region size

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

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

From: Ard Biesheuvel <ard.biesheuvel@...aro.org>

commit 34ba2c4247e5c4b1542b1106e156af324660c4f0 upstream.

The linear region size of a 39-bit VA kernel is only 256 GB, which
may be insufficient to cover all of system RAM, even on platforms
that have much less than 256 GB of memory but which is laid out
very sparsely.

So make sure we clip the memory we will not be able to map before
installing it into the memblock memory table, by setting
MAX_MEMBLOCK_ADDR accordingly.

Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Tested-by: Stuart Yoder <stuart.yoder@...escale.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/include/asm/memory.h |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -114,6 +114,14 @@ extern phys_addr_t		memstart_addr;
 #define PHYS_OFFSET		({ memstart_addr; })
 
 /*
+ * The maximum physical address that the linear direct mapping
+ * of system RAM can cover. (PAGE_OFFSET can be interpreted as
+ * a 2's complement signed quantity and negated to derive the
+ * maximum size of the linear mapping.)
+ */
+#define MAX_MEMBLOCK_ADDR	({ memstart_addr - PAGE_OFFSET - 1; })
+
+/*
  * PFNs are used to describe any physical page; this means
  * PFN 0 == physical address 0.
  *


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