[PATCH] [v2] powerpc/4xx: work around CHIP11 errata in a more PAGE_SIZE-friendly way

The current CHIP11 errata truncates the device tree memory node, and subtracts
(hardcoded) 4096 bytes. This breaks kernels with larger PAGE_SIZE, since the
bootmem allocator assumes that total memory is a multiple of PAGE_SIZE.

Instead, use a device tree memory reservation to reserve only the 256 bytes
actually affected by the errata, leaving the total memory size unaltered.

Signed-off-by: Hollis Blanchard <redacted>

---

Using large pages results in a huge performance improvement for KVM, and this
patch is required to make Ilya's large page patch work. David and/or Josh,
please apply.

diff --git a/arch/powerpc/boot/4xx.c b/arch/powerpc/boot/4xx.c
--- a/arch/powerpc/boot/4xx.c
+++ b/arch/powerpc/boot/4xx.c

@@ -21,7 +21,7 @@
 #include "reg.h"
 #include "dcr.h"
 
-static unsigned long chip_11_errata(unsigned long memsize)
+static void chip_11_errata(unsigned long memsize)
 {
 	unsigned long pvr;
 

@@ -31,13 +31,11 @@ static unsigned long chip_11_errata(unsi
 		case 0x40000850:
 		case 0x400008d0:
 		case 0x200008d0:
-			memsize -= 4096;
+			fdt_add_mem_rsv(fdt, memsize - 256, 256);
 			break;
 		default:
 			break;
 	}
-
-	return memsize;
 }
 
 /* Read the 4xx SDRAM controller to get size of system memory. */

@@ -53,7 +51,7 @@ void ibm4xx_sdram_fixup_memsize(void)
 			memsize += SDRAM_CONFIG_BANK_SIZE(bank_config);
 	}
 
-	memsize = chip_11_errata(memsize);
+	chip_11_errata(memsize);
 	dt_fixup_memory(0, memsize);
 }
 

@@ -219,7 +217,7 @@ void ibm4xx_denali_fixup_memsize(void)
 		bank = 4; /* 4 banks */
 
 	memsize = cs * (1 << (col+row)) * bank * dpath;
-	memsize = chip_11_errata(memsize);
+	chip_11_errata(memsize);
 	dt_fixup_memory(0, memsize);
 }
 

diff --git a/arch/powerpc/boot/libfdt-wrapper.c b/arch/powerpc/boot/libfdt-wrapper.c
--- a/arch/powerpc/boot/libfdt-wrapper.c
+++ b/arch/powerpc/boot/libfdt-wrapper.c

@@ -51,7 +51,7 @@
 #define devp_offset_find(devp)	(((int)(devp))-1)
 #define devp_offset(devp)	(devp ? ((int)(devp))-1 : 0)
 
-static void *fdt;
+void *fdt;
 static void *buf; /* = NULL */
 
 #define EXPAND_GRANULARITY	1024

diff --git a/arch/powerpc/boot/ops.h b/arch/powerpc/boot/ops.h
--- a/arch/powerpc/boot/ops.h
+++ b/arch/powerpc/boot/ops.h

@@ -14,6 +14,7 @@
 #include <stddef.h>
 #include "types.h"
 #include "string.h"
+#include "libfdt_env.h"
 
 #define	COMMAND_LINE_SIZE	512
 #define	MAX_PATH_LEN		256

@@ -32,6 +33,9 @@ struct platform_ops {
 	void *	(*vmlinux_alloc)(unsigned long size);
 };
 extern struct platform_ops platform_ops;
+
+/* The device tree itself. Should almost always be accessed via dt_ops. */
+extern void *fdt;
 
 /* Device Tree operations */
 struct dt_ops {

@@ -98,6 +102,8 @@ void dt_get_reg_format(void *node, u32 *
 void dt_get_reg_format(void *node, u32 *naddr, u32 *nsize);
 int dt_get_virtual_reg(void *node, void **addr, int nres);
 
+int fdt_add_mem_rsv(void *fdt, uint64_t address, uint64_t size);
+
 static inline void *finddevice(const char *name)
 {
 	return (dt_ops.finddevice) ? dt_ops.finddevice(name) : NULL;

On Mon, Nov 10, 2008 at 05:24:34PM -0600, Hollis Blanchard wrote:

The current CHIP11 errata truncates the device tree memory node, and subtracts
(hardcoded) 4096 bytes. This breaks kernels with larger PAGE_SIZE, since the
bootmem allocator assumes that total memory is a multiple of PAGE_SIZE.

Instead, use a device tree memory reservation to reserve only the 256 bytes
actually affected by the errata, leaving the total memory size unaltered.

Signed-off-by: Hollis Blanchard <redacted>

---

Using large pages results in a huge performance improvement for KVM, and this
patch is required to make Ilya's large page patch work. David and/or Josh,
please apply.

The patch looks fine to me, and once David acks the fdt parts I'll apply
for -next.  I'll try to do some testing later today as well, since I have
one of the boards with the Errata.

josh

52 more quoted lines

On Tue, Nov 11, 2008 at 07:52:18AM -0500, Josh Boyer wrote:

On Mon, Nov 10, 2008 at 05:24:34PM -0600, Hollis Blanchard wrote:

quoted

The current CHIP11 errata truncates the device tree memory node, and subtracts
(hardcoded) 4096 bytes. This breaks kernels with larger PAGE_SIZE, since the
bootmem allocator assumes that total memory is a multiple of PAGE_SIZE.

Instead, use a device tree memory reservation to reserve only the 256 bytes
actually affected by the errata, leaving the total memory size unaltered.

Signed-off-by: Hollis Blanchard <redacted>

---

Using large pages results in a huge performance improvement for KVM, and this
patch is required to make Ilya's large page patch work. David and/or Josh,
please apply.

The patch looks fine to me, and once David acks the fdt parts I'll apply
for -next.  I'll try to do some testing later today as well, since I have
one of the boards with the Errata.

Um.. I sent something the fdt stuff a while back, but didn't get a
response.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson