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Subject[PATCH 02/50] x86/boot/e820: Clean up and improve comments in asm/e820/types.h
Date
Do some common-sense cleanups:

- standardize on the kernel coding style consistently

- tabulate definitions consistently

- extend and clarify various descriptions

- fix speling

- update the header guard name according to the new position

- etc.

No change in functionality.

Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Jackson <pj@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/e820/types.h | 84 +++++++++++++++++++++++++++++++++++++----------------------
1 file changed, 53 insertions(+), 31 deletions(-)

diff --git a/arch/x86/include/asm/e820/types.h b/arch/x86/include/asm/e820/types.h
index 9dafe59cf6e2..cfa8f4a19b5d 100644
--- a/arch/x86/include/asm/e820/types.h
+++ b/arch/x86/include/asm/e820/types.h
@@ -1,18 +1,30 @@
-#ifndef _UAPI_ASM_X86_E820_H
-#define _UAPI_ASM_X86_E820_H
-#define E820MAP 0x2d0 /* our map */
-#define E820MAX 128 /* number of entries in E820MAP */
+#ifndef _ASM_E820_TYPES_H
+#define _ASM_E820_TYPES_H
+
+/* Our map: */
+#define E820MAP 0x2d0
+
+/* The maximum number of entries in E820MAP: */
+#define E820MAX 128

/*
- * Legacy E820 BIOS limits us to 128 (E820MAX) nodes due to the
- * constrained space in the zeropage. If we have more nodes than
- * that, and if we've booted off EFI firmware, then the EFI tables
- * passed us from the EFI firmware can list more nodes. Size our
- * internal memory map tables to have room for these additional
- * nodes, based on up to three entries per node for which the
- * kernel was built: MAX_NUMNODES == (1 << CONFIG_NODES_SHIFT),
- * plus E820MAX, allowing space for the possible duplicate E820
- * entries that might need room in the same arrays, prior to the
+ * The legacy E820 BIOS limits us to 128 (E820MAX) nodes due to the
+ * constrained space in the zeropage.
+ *
+ * On large systems we can easily have thousands of nodes with RAM,
+ * which cannot be fit into so few entries - so we have a mechanism
+ * to extend the e820 table size at build-time, via the E820_X_MAX
+ * define below.
+ *
+ * ( Those extra entries are enumerated via the EFI memory map, not
+ * via the legacy zeropage mechanism. )
+ *
+ * Size our internal memory map tables to have room for these additional
+ * entries, based on a heuristic calculation: up to three entries per
+ * NUMA node, plus E820MAX for some extra space.
+ *
+ * This allows for bootstrap/firmware quirks such as possible duplicate
+ * E820 entries that might need room in the same arrays, prior to the
* call to sanitize_e820_map() to remove duplicates. The allowance
* of three memory map entries per node is "enough" entries for
* the initial hardware platform motivating this mechanism to make
@@ -20,19 +32,19 @@
* to allow more than three entries per node or otherwise refine
* this size.
*/
-
#ifndef __KERNEL__
-#define E820_X_MAX E820MAX
+# define E820_X_MAX E820MAX
#endif

-#define E820NR 0x1e8 /* # entries in E820MAP */
+/* Number of entries in E820MAP: */
+#define E820NR 0x1e8

-#define E820_RAM 1
-#define E820_RESERVED 2
-#define E820_ACPI 3
-#define E820_NVS 4
-#define E820_UNUSABLE 5
-#define E820_PMEM 7
+#define E820_RAM 1
+#define E820_RESERVED 2
+#define E820_ACPI 3
+#define E820_NVS 4
+#define E820_UNUSABLE 5
+#define E820_PMEM 7

/*
* This is a non-standardized way to represent ADR or NVDIMM regions that
@@ -43,7 +55,7 @@
* but newer versions switched to 12 as 6 was assigned differently. Some
* time they will learn... )
*/
-#define E820_PRAM 12
+#define E820_PRAM 12

/*
* reserved RAM used by kernel itself
@@ -51,23 +63,34 @@
* included in the S3 integrity calculation and so should not include
* any memory that BIOS might alter over the S3 transition
*/
-#define E820_RESERVED_KERN 128
+#define E820_RESERVED_KERN 128

#ifndef __ASSEMBLY__
#include <linux/types.h>
+
+/*
+ * A single E820 map entry, describing a memory range of [addr...addr+size-1],
+ * of 'type' memory type:
+ */
struct e820entry {
- __u64 addr; /* start of memory segment */
- __u64 size; /* size of memory segment */
- __u32 type; /* type of memory segment */
+ __u64 addr;
+ __u64 size;
+ __u32 type;
} __attribute__((packed));

+/*
+ * The whole array of E820 entries:
+ */
struct e820map {
__u32 nr_map;
struct e820entry map[E820_X_MAX];
};

-#define ISA_START_ADDRESS 0xa0000
-#define ISA_END_ADDRESS 0x100000
+/*
+ * Various legacy ranges in physical memory:
+ */
+#define ISA_START_ADDRESS 0x000a0000
+#define ISA_END_ADDRESS 0x00100000

#define BIOS_BEGIN 0x000a0000
#define BIOS_END 0x00100000
@@ -77,5 +100,4 @@ struct e820map {

#endif /* __ASSEMBLY__ */

-
-#endif /* _UAPI_ASM_X86_E820_H */
+#endif /* _ASM_E820_TYPES_H */
--
2.7.4
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