[Xen-devel] [PATCH 1/2] x86: Make E820_X_MAX unconditionally larger than E820MAX

[Alex Thorlton <athorlton@xxxxxxx>]

It's really not necessary to limit E820_X_MAX to 128 in the non-EFI
case.  This commit drops E820_X_MAX's dependency on CONFIG_EFI, so that
E820_X_MAX is always at least slightly larger than E820MAX.

The real motivation behind this is actually to prevent some issues in
the Xen kernel, where the XENMEM_machine_memory_map hypercall can
produce an e820 map larger than 128 entries, even on systems where the
original e820 table was quite a bit smaller than that, depending on how
many IOAPICs are installed on the system.

Signed-off-by: Alex Thorlton <athorlton@xxxxxxx>
Suggested-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Russ Anderson <rja@xxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
---
 arch/x86/include/asm/e820.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/e820.h b/arch/x86/include/asm/e820.h
index 476b574..ec23d8e 100644
--- a/arch/x86/include/asm/e820.h
+++ b/arch/x86/include/asm/e820.h
@@ -1,13 +1,17 @@
 #ifndef _ASM_X86_E820_H
 #define _ASM_X86_E820_H
 
-#ifdef CONFIG_EFI
+/*
+ * E820_X_MAX is the maximum size of the extended E820 table.  The extended
+ * table may contain up to 3 extra E820 entries per possible NUMA node, so we
+ * make room for 3 * MAX_NUMNODES possible entries, beyond the standard 128.
+ * Also note that E820_X_MAX *must* be defined before we include 
uapi/asm/e820.h.
+ */
 #include <linux/numa.h>
 #define E820_X_MAX (E820MAX + 3 * MAX_NUMNODES)
-#else  /* ! CONFIG_EFI */
-#define E820_X_MAX E820MAX
-#endif
+
 #include <uapi/asm/e820.h>
+
 #ifndef __ASSEMBLY__
 /* see comment in arch/x86/kernel/e820.c */
 extern struct e820map *e820;
-- 
1.8.5.6


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