[PATCH] x86, kexec: Limit the crashkernel address to 512 MiB

[H . Peter Anvin]

We used to only map a maximum of 512 MiB of low memory for the kernel
initialization; this was enforced by the bzImage decompressor.  To
make sure we do not run afoul of this limitation, keep the crash
kernel below the 512 MiB mark.

This also adds a comfortable margin in case the user is running with a
nonstandard vmalloc= setting.

Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
LKML-Reference: <4D09958D.2040907@xxxxxxxxxx>
---
 arch/x86/kernel/setup.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 21c6746..7fb9abb 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -501,7 +501,12 @@ static inline unsigned long long get_total_mem(void)
 	return total << PAGE_SHIFT;
 }
 
-#define DEFAULT_BZIMAGE_ADDR_MAX 0x37FFFFFF
+/*
+ * Keep the crash kernel below this limit.  Not all bzImage kernels
+ * can be loaded above this address.
+ */
+#define CRASH_KERNEL_ADDR_MAX	(512 << 20)
+
 static void __init reserve_crashkernel(void)
 {
 	unsigned long long total_mem;
@@ -520,10 +525,10 @@ static void __init reserve_crashkernel(void)
 		const unsigned long long alignment = 16<<20;	/* 16M */
 
 		/*
-		 *  kexec want bzImage is below DEFAULT_BZIMAGE_ADDR_MAX
+		 *  kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
 		 */
 		crash_base = memblock_find_in_range(alignment,
-			       DEFAULT_BZIMAGE_ADDR_MAX, crash_size, alignment);
+			       CRASH_KERNEL_ADDR_MAX, crash_size, alignment);
 
 		if (crash_base == MEMBLOCK_ERROR) {
 			pr_info("crashkernel reservation failed - No suitable area found.\n");
-- 
1.7.2.3


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