Increase number of e820 entries hard limit from 32 to 128

The specifications that talk about E820 map doesn't have an upper limit on the number of E820 entries. But, today's kernel has a hard limit of 32. With increase in memory size, we are seeing the number of E820 entries reaching close to 32. Patch below bumps the number upto 128.

Patch does it for both i386 and x86-64.

Side-effect: bss increases by ~ 2K and init.data increases by ~7.5K on all systems, due to increase in size of static arrays.

Signed-off-by Venkatesh Pallipadi <[email protected]>

diff -purN linux-2.6.11/Documentation/i386/zero-page.txt.orig linux-2.6.11/Documentation/i386/zero-page.txt

Documentation/i386/zero-page.txt renamed from Documentation/i386/zero-page.txt.orig +0 -0

@@ -79,6 +79,6 @@ Offset	Type		Description

0x22c unsigned long ramdisk_max
0x230 16 bytes trampoline
0x290 - 0x2cf EDD_MBR_SIG_BUFFER (edd.S)
-0x2d0 - 0x600 E820MAP
-0x600 - 0x7ff EDDBUF (edd.S) for disk signature read sector
-0x600 - 0x7eb EDDBUF (edd.S) for edd data
+0x2d0 - 0xd00 E820MAP
+0xd00 - 0xeff EDDBUF (edd.S) for disk signature read sector
+0xd00 - 0xeeb EDDBUF (edd.S) for edd data
diff -purN linux-2.6.11/include/linux/edd.h.orig linux-2.6.11/include/linux/edd.h

include/linux/edd.h renamed from include/linux/edd.h.orig +1 -1

@@ -32,7 +32,7 @@
 
 #define EDDNR 0x1e9		/* addr of number of edd_info structs at EDDBUF
 				   in boot_params - treat this as 1 byte  */
-#define EDDBUF	0x600		/* addr of edd_info structs in boot_params */
+#define EDDBUF	0xd00		/* addr of edd_info structs in boot_params */
 #define EDDMAXNR 6		/* number of edd_info structs starting at EDDBUF  */
 #define EDDEXTSIZE 8		/* change these if you muck with the structures */
 #define EDDPARMSIZE 74

diff -purN linux-2.6.11/include/asm-i386/e820.h.orig linux-2.6.11/include/asm-i386/e820.h

include/asm-i386/e820.h renamed from include/asm-i386/e820.h.orig +1 -1

@@ -13,7 +13,7 @@
 #define __E820_HEADER
 
 #define E820MAP	0x2d0		/* our map */
-#define E820MAX	32		/* number of entries in E820MAP */
+#define E820MAX	128		/* number of entries in E820MAP */
 #define E820NR	0x1e8		/* # entries in E820MAP */
 
 #define E820_RAM	1

diff -purN linux-2.6.11/include/asm-i386/setup.h.orig linux-2.6.11/include/asm-i386/setup.h

include/asm-i386/setup.h renamed from include/asm-i386/setup.h.orig +1 -1

@@ -16,7 +16,7 @@
 #define MAXMEM_PFN	PFN_DOWN(MAXMEM)
 #define MAX_NONPAE_PFN	(1 << 20)
 
-#define PARAM_SIZE 2048
+#define PARAM_SIZE 4096
 #define COMMAND_LINE_SIZE 256
 
 #define OLD_CL_MAGIC_ADDR	0x90020

diff -purN linux-2.6.11/arch/i386/boot/setup.S.orig linux-2.6.11/arch/i386/boot/setup.S

arch/i386/boot/setup.S renamed from arch/i386/boot/setup.S.orig +0 -0

@@ -164,7 +164,7 @@ ramdisk_max:	.long (-__PAGE_OFFSET-(512 

trampoline: call start_of_setup

		.align 16
					# The offset at this point is 0x240

arch/i386/boot/setup.S renamed from arch/i386/boot/setup.S.orig +1 -1

-		.space	(0x7ff-0x240+1) # E820 & EDD space (ending at 0x7ff)
+		.space	(0xeff-0x240+1) # E820 & EDD space (ending at 0xeff)

# End of setup header #####################################################

start_of_setup:

arch/i386/boot/setup.S renamed from arch/i386/boot/setup.S.orig +0 -0

@@ -333,9 +333,9 @@ jmpe820:
 	# sizeof(e820rec).
 	#

good820:

arch/i386/boot/setup.S renamed from arch/i386/boot/setup.S.orig +1 -1

-	movb	(E820NR), %al			# up to 32 entries
+	movb	(E820NR), %al			# up to 128 entries

	cmpb	$E820MAX, %al

arch/i386/boot/setup.S renamed from arch/i386/boot/setup.S.orig +1 -1

-	jnl	bail820
+	jae	bail820

	incb	(E820NR)
	movw	%di, %ax

diff -purN linux-2.6.11/include/asm-x86_64/e820.h.orig linux-2.6.11/include/asm-x86_64/e820.h

include/asm-x86_64/e820.h renamed from include/asm-x86_64/e820.h.orig +1 -1

@@ -14,7 +14,7 @@
 #include <linux/mmzone.h>
 
 #define E820MAP	0x2d0		/* our map */
-#define E820MAX	32		/* number of entries in E820MAP */
+#define E820MAX	128		/* number of entries in E820MAP */
 #define E820NR	0x1e8		/* # entries in E820MAP */
 
 #define E820_RAM	1

diff -purN linux-2.6.11/include/asm-x86_64/bootsetup.h.orig linux-2.6.11/include/asm-x86_64/bootsetup.h

include/asm-x86_64/bootsetup.h renamed from include/asm-x86_64/bootsetup.h.orig +2 -1

@@ -2,7 +2,8 @@
 #ifndef _X86_64_BOOTSETUP_H
 #define _X86_64_BOOTSETUP_H 1
 
-extern char x86_boot_params[2048];
+#define BOOT_PARAM_SIZE		4096
+extern char x86_boot_params[BOOT_PARAM_SIZE];
 
 /*
 * This is set up by the setup-routine at boot-time

diff -purN linux-2.6.11/arch/x86_64/boot/setup.S.orig linux-2.6.11/arch/x86_64/boot/setup.S

arch/x86_64/boot/setup.S renamed from arch/x86_64/boot/setup.S.orig +0 -0

@@ -160,7 +160,7 @@ ramdisk_max:	.long 0xffffffff

trampoline: call start_of_setup

		.align 16
					# The offset at this point is 0x240

arch/x86_64/boot/setup.S renamed from arch/x86_64/boot/setup.S.orig +1 -1

-		.space  (0x7ff-0x240+1)	# E820 & EDD space (ending at 0x7ff)
+		.space  (0xeff-0x240+1)	# E820 & EDD space (ending at 0xeff)

# End of setup header #####################################################

start_of_setup:

arch/x86_64/boot/setup.S renamed from arch/x86_64/boot/setup.S.orig +0 -0

@@ -412,9 +412,9 @@ jmpe820:
 	# sizeof(e820rec).
 	#

good820:

arch/x86_64/boot/setup.S renamed from arch/x86_64/boot/setup.S.orig +1 -1

-	movb	(E820NR), %al			# up to 32 entries
+	movb	(E820NR), %al			# up to 128 entries

	cmpb	$E820MAX, %al

arch/x86_64/boot/setup.S renamed from arch/x86_64/boot/setup.S.orig +1 -1

-	jnl	bail820
+	jae	bail820

	incb	(E820NR)
	movw	%di, %ax

diff -purN linux-2.6.11/arch/x86_64/kernel/setup64.c.orig linux-2.6.11/arch/x86_64/kernel/setup64.c

arch/x86_64/kernel/setup64.c renamed from arch/x86_64/kernel/setup64.c.orig +2 -1

@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/bootmem.h>
 #include <linux/bitops.h>
+#include <asm/bootsetup.h>
 #include <asm/pda.h>
 #include <asm/pgtable.h>
 #include <asm/processor.h>

@@ -26,7 +27,7 @@
 #include <asm/mman.h>
 #include <asm/numa.h>
 
-char x86_boot_params[2048] __initdata = {0,};
+char x86_boot_params[BOOT_PARAM_SIZE] __initdata = {0,};
 
 cpumask_t cpu_initialized __initdata = CPU_MASK_NONE;
 

diff -purN linux-2.6.11/arch/x86_64/kernel/head64.c.orig linux-2.6.11/arch/x86_64/kernel/head64.c

arch/x86_64/kernel/head64.c renamed from arch/x86_64/kernel/head64.c.orig +1 -4

@@ -29,8 +29,6 @@ static void __init clear_bss(void)
 	       (unsigned long) __bss_end - (unsigned long) __bss_start);
 }
 
-extern char x86_boot_params[2048];
-
 #define NEW_CL_POINTER		0x228	/* Relative to real mode data */
 #define OLD_CL_MAGIC_ADDR	0x90020
 #define OLD_CL_MAGIC            0xA33F

@@ -44,7 +42,7 @@ static void __init copy_bootdata(char *r
 	int new_data;
 	char * command_line;
 
-	memcpy(x86_boot_params, real_mode_data, 2048); 
+	memcpy(x86_boot_params, real_mode_data, BOOT_PARAM_SIZE); 
 	new_data = *(int *) (x86_boot_params + NEW_CL_POINTER);
 	if (!new_data) {
 		if (OLD_CL_MAGIC != * (u16 *) OLD_CL_MAGIC_ADDR) {
-

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The specifications that talk about E820 map doesn't have an upper limit on the number of E820 entries. But, today's kernel has a hard limit of 32. With increase in memory size, we are seeing the number of E820 entries reaching close to 32. Patch below bumps the number upto 128.

Quoted 4 lines · Venkatesh Pallipadi

The specifications that talk about E820 map doesn't have an upper limit on the number of E820 entries. But, today's kernel has a hard limit of 32. With increase in memory size, we are seeing the number of E820 entries reaching close to 32. Patch below bumps the number upto 128.

Hmm. Anything that changes setup.S tends to have bootloader dependencies. I worry whether this one does too..

Quoted 6 lines · Linus Torvalds

Quoted 4 lines · Venkatesh Pallipadi

The specifications that talk about E820 map doesn't have an upper limit on the number of E820 entries. But, today's kernel has a hard limit of 32. With increase in memory size, we are seeing the number of E820 entries reaching close to 32. Patch below bumps the number upto 128.

Quoted 3 lines

Hmm. Anything that changes setup.S tends to have bootloader dependencies. I worry whether this one does too..

The setup.S change in this patch should be OK. As it is adding to the existing zero-page and keeping it within one page. I tested it on systems with grub, adding some dummy E820 entries and it worked fine.

Quoted 11 lines · Venkatesh Pallipadi

Quoted 9 lines · Linus Torvalds

Quoted 4 lines · Venkatesh Pallipadi

The specifications that talk about E820 map doesn't have an upper limit on the number of E820 entries. But, today's kernel has a hard limit of 32. With increase in memory size, we are seeing the number of E820 entries reaching close to 32. Patch below bumps the number upto 128.

Hmm. Anything that changes setup.S tends to have bootloader dependencies. I worry whether this one does too..

Quoted 3 lines

The setup.S change in this patch should be OK. As it is adding to the existing zero-page and keeping it within one page. I tested it on systems with grub, adding some dummy E820 entries and it worked fine.

The last time I tried to extend the zero page (with a longer command line) it broke lilo on systems with EDID support and CONFIG_EDID enabled. Make sure you test that case.

The last time I tried to extend the zero page (with a longer command line) it broke lilo on systems with EDID support and CONFIG_EDID enabled. Make sure you test that case.