diff mbox

[v2] powerpc 44x: support for 256KB PAGE_SIZE

Message ID 200812211446.56783.yur@emcraft.com (mailing list archive)
State Superseded, archived
Delegated to: Josh Boyer
Headers show

Commit Message

Yuri Tikhonov Dec. 21, 2008, 11:46 a.m. UTC 
This patch adds support for 256KB pages on ppc44x-based boards.

For simplification of implementation with 256KB pages we still assume
2-level paging. As a side effect this leads to wasting extra memory space
reserved for PTE tables: only 1/4 of pages allocated for PTEs are
actually used. But this may be an acceptable trade-off to achieve the
high performance we have with big PAGE_SIZEs in some applications (e.g.
RAID).

Also with 256KB PAGE_SIZE we increase THREAD_SIZE up to 32KB to minimize
the risk of stack overflows in the cases of on-stack arrays, which size
depends on the page size (e.g. multipage BIOs, NTFS, etc.).

With 256KB PAGE_SIZE we need to decrease the PKMAP_ORDER at least down
to 9, otherwise all high memory (2 ^ 10 * PAGE_SIZE == 256MB) we'll be
occupied by PKMAP addresses leaving no place for vmalloc. We do not
separate PKMAP_ORDER for 256K from 16K/64K PAGE_SIZE here; actually that
value of 10 in support for 16K/64K had been selected rather intuitively.
Thus now for all cases of PAGE_SIZE on ppc44x (including the default, 4KB,
one) we have 512 pages for PKMAP.

Because ELF standard supports only page sizes up to 64K, then you should
use patched binutils for building applications to be run with the 256KB-
page sized kernel. The patch for binutils is rather trivial, and may
look as follows:

--- binutils/bfd/elf32-ppc.c.orig
+++ binutils/bfd/elf32-ppc.c

-#define ELF_MAXPAGESIZE                0x10000
+#define ELF_MAXPAGESIZE                0x40000

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Ilya Yanok <yanok@emcraft.com>
---
 arch/powerpc/Kconfig                   |   14 ++++++++++++++
 arch/powerpc/include/asm/highmem.h     |   10 +++++-----
 arch/powerpc/include/asm/mmu-44x.h     |    2 ++
 arch/powerpc/include/asm/page.h        |    6 ++++--
 arch/powerpc/include/asm/page_32.h     |    4 ++++
 arch/powerpc/include/asm/thread_info.h |    4 +++-
 arch/powerpc/kernel/head_booke.h       |   11 ++++++++++-
 arch/powerpc/platforms/44x/Kconfig     |   10 ++++++++++
 8 files changed, 52 insertions(+), 9 deletions(-)

Comments

Andreas Schwab Dec. 21, 2008, 5:07 p.m. UTC | #1 
Yuri Tikhonov <yur@emcraft.com> writes:

> Because ELF standard supports only page sizes up to 64K, then you should
> use patched binutils for building applications to be run with the 256KB-
> page sized kernel. The patch for binutils is rather trivial, and may
> look as follows:
>
> --- binutils/bfd/elf32-ppc.c.orig
> +++ binutils/bfd/elf32-ppc.c
>
> -#define ELF_MAXPAGESIZE                0x10000
> +#define ELF_MAXPAGESIZE                0x40000

You don't have to patch it, it's enough to pass -zmax-page-size=0x40000
to the linker.

Andreas.
Yuri Tikhonov Dec. 21, 2008, 8 p.m. UTC | #2 
Hello Andreas,

On Sunday, December 21, 2008 you wrote:

> Yuri Tikhonov <yur@emcraft.com> writes:

>> Because ELF standard supports only page sizes up to 64K, then you should
>> use patched binutils for building applications to be run with the 256KB-
>> page sized kernel. The patch for binutils is rather trivial, and may
>> look as follows:
>>
>> --- binutils/bfd/elf32-ppc.c.orig
>> +++ binutils/bfd/elf32-ppc.c
>>
>> -#define ELF_MAXPAGESIZE                0x10000
>> +#define ELF_MAXPAGESIZE                0x40000

> You don't have to patch it, it's enough to pass -zmax-page-size=0x40000
> to the linker.

 Thanks for pointing this. I guess, the -zmax-page-size option is new 
to binutils 2.17.50.0.10. Right?

 I'll remove the STDBINUTILS config option from this patch then, and 
correspondingly update the description.

 Regards, Yuri

 --
 Yuri Tikhonov, Senior Software Engineer
 Emcraft Systems, www.emcraft.com
Andreas Schwab Dec. 21, 2008, 8:14 p.m. UTC | #3 
Yuri Tikhonov <yur@emcraft.com> writes:

>  Thanks for pointing this. I guess, the -zmax-page-size option is new 
> to binutils 2.17.50.0.10. Right?

It was added 2½ years ago.

Andreas.
Yuri Tikhonov Dec. 21, 2008, 8:35 p.m. UTC | #4 
On Sunday, December 21, 2008 you wrote:

> Yuri Tikhonov <yur@emcraft.com> writes:

>>  Thanks for pointing this. I guess, the -zmax-page-size option is new 
>> to binutils 2.17.50.0.10. Right?

> It was added 2½ years ago.

 Yes, approximately: http://gcc.gnu.org/ml/gcc/2006-07/msg00361.html

"
Date: Sat, 15 Jul 2006 15:19:05 -0700
Subject: The Linux binutils 2.17.50.0.3 is released

Changes from binutils 2.17.50.0.2:
...
16. Add "-z max-page-size=" and "-z common-page-size=" to ELF linker.
"

>>  I'll remove the STDBINUTILS config option from this patch then, and 
>> correspondingly update the description.

 I thought about this more, and I guess that we should keep the 
dependency on the newly introduced by this patch STDBINUTILS option. 
Perhaps, change it name to, say, STD_ELF_LINKING.

 Because, in any case, either should we patch binutils, or should we 
pass some non-default value to the linker: the resulted application 
doesn't match the ELF standard, and the applications which match the 
standard simply won't work with the 256K paged kernel - so, a user has 
to be aware of it before turning the 256K on.

 What do you think about this?

 Regards, Yuri
Andreas Schwab Dec. 21, 2008, 8:57 p.m. UTC | #5 
Yuri Tikhonov <yur@emcraft.com> writes:

>  Because, in any case, either should we patch binutils, or should we 
> pass some non-default value to the linker: the resulted application 
> doesn't match the ELF standard

An ELF object built with a 256k alignment of is still perfectly
compliant.

Andreas.
diff mbox

Patch

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index cd8ff7c..3338e71 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -436,6 +436,18 @@  config PPC_64K_PAGES
 	bool "64k page size" if 44x || PPC_STD_MMU_64
 	select PPC_HAS_HASH_64K if PPC_STD_MMU_64
 
+config PPC_256K_PAGES
+	bool "256k page size" if 44x
+	depends on !STDBINUTILS
+	help
+	  Make the page size 256k.
+
+	  As the ELF standard only requires alignment to support page
+	  sizes up to 64k, you will need to compile all of your user
+	  space applications with a patched binutils.
+
+	  Say N unless you know what you are doing.
+
 endchoice
 
 config FORCE_MAX_ZONEORDER
@@ -448,6 +460,8 @@  config FORCE_MAX_ZONEORDER
 	default "9" if PPC_STD_MMU_32 && PPC_16K_PAGES
 	range 7 64 if PPC_STD_MMU_32 && PPC_64K_PAGES
 	default "7" if PPC_STD_MMU_32 && PPC_64K_PAGES
+	range 5 64 if PPC_STD_MMU_32 && PPC_256K_PAGES
+	default "5" if PPC_STD_MMU_32 && PPC_256K_PAGES
 	range 11 64
 	default "11"
 	help
diff --git a/arch/powerpc/include/asm/highmem.h b/arch/powerpc/include/asm/highmem.h
index 7d6bb37..0d1333f 100644
--- a/arch/powerpc/include/asm/highmem.h
+++ b/arch/powerpc/include/asm/highmem.h
@@ -39,15 +39,15 @@  extern pte_t *pkmap_page_table;
  * chunk of RAM.
  */
 /*
- * We use one full pte table with 4K pages. And with 16K/64K pages pte
- * table covers enough memory (32MB and 512MB resp.) that both FIXMAP
- * and PKMAP can be placed in single pte table. We use 1024 pages for
- * PKMAP in case of 16K/64K pages.
+ * We use one full pte table with 4K pages. And with 16K/64K/256K pages pte
+ * table covers enough memory (32MB/512MB/2GB resp.), so that both FIXMAP
+ * and PKMAP can be placed in a single pte table. We use 512 pages for PKMAP
+ * in case of 16K/64K/256K page sizes.
  */
 #ifdef CONFIG_PPC_4K_PAGES
 #define PKMAP_ORDER	PTE_SHIFT
 #else
-#define PKMAP_ORDER	10
+#define PKMAP_ORDER	9
 #endif
 #define LAST_PKMAP	(1 << PKMAP_ORDER)
 #ifndef CONFIG_PPC_4K_PAGES
diff --git a/arch/powerpc/include/asm/mmu-44x.h b/arch/powerpc/include/asm/mmu-44x.h
index 73e1909..52a2339 100644
--- a/arch/powerpc/include/asm/mmu-44x.h
+++ b/arch/powerpc/include/asm/mmu-44x.h
@@ -81,6 +81,8 @@  typedef struct {
 #define PPC44x_TLBE_SIZE	PPC44x_TLB_16K
 #elif (PAGE_SHIFT == 16)
 #define PPC44x_TLBE_SIZE	PPC44x_TLB_64K
+#elif (PAGE_SHIFT == 18)
+#define PPC44x_TLBE_SIZE	PPC44x_TLB_256K
 #else
 #error "Unsupported PAGE_SIZE"
 #endif
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 197d569..32cbf16 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -19,12 +19,14 @@ 
 #include <asm/kdump.h>
 
 /*
- * On regular PPC32 page size is 4K (but we support 4K/16K/64K pages
+ * On regular PPC32 page size is 4K (but we support 4K/16K/64K/256K pages
  * on PPC44x). For PPC64 we support either 4K or 64K software
  * page size. When using 64K pages however, whether we are really supporting
  * 64K pages in HW or not is irrelevant to those definitions.
  */
-#if defined(CONFIG_PPC_64K_PAGES)
+#if defined(CONFIG_PPC_256K_PAGES)
+#define PAGE_SHIFT		18
+#elif defined(CONFIG_PPC_64K_PAGES)
 #define PAGE_SHIFT		16
 #elif defined(CONFIG_PPC_16K_PAGES)
 #define PAGE_SHIFT		14
diff --git a/arch/powerpc/include/asm/page_32.h b/arch/powerpc/include/asm/page_32.h
index 1458d95..a0e3f6e 100644
--- a/arch/powerpc/include/asm/page_32.h
+++ b/arch/powerpc/include/asm/page_32.h
@@ -19,7 +19,11 @@ 
 #define PTE_FLAGS_OFFSET	0
 #endif
 
+#ifdef CONFIG_PPC_256K_PAGES
+#define PTE_SHIFT	(PAGE_SHIFT - PTE_T_LOG2 - 2)	/* 1/4 of a page */
+#else
 #define PTE_SHIFT	(PAGE_SHIFT - PTE_T_LOG2)	/* full page */
+#endif
 
 #ifndef __ASSEMBLY__
 /*
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 9665a26..e04286f 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -12,8 +12,10 @@ 
 
 /* We have 8k stacks on ppc32 and 16k on ppc64 */
 
-#ifdef CONFIG_PPC64
+#if defined(CONFIG_PPC64)
 #define THREAD_SHIFT		14
+#elif defined(CONFIG_PPC_256K_PAGES)
+#define THREAD_SHIFT		15
 #else
 #define THREAD_SHIFT		13
 #endif
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index fce2df9..17803ad 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -10,6 +10,15 @@ 
 		mtspr	SPRN_IVOR##vector_number,r26;	\
 		sync
 
+#if (THREAD_SHIFT < 15)
+#define ALLOC_STACK_FRAME(reg, val)			\
+	addi reg,reg,val
+#else
+#define ALLOC_STACK_FRAME(reg, val)			\
+	addis	reg,reg,val@ha;				\
+	addi	reg,reg,val@l
+#endif
+
 #define NORMAL_EXCEPTION_PROLOG						     \
 	mtspr	SPRN_SPRG0,r10;		/* save two registers to work with */\
 	mtspr	SPRN_SPRG1,r11;						     \
@@ -20,7 +29,7 @@ 
 	beq	1f;							     \
 	mfspr	r1,SPRN_SPRG3;		/* if from user, start at top of   */\
 	lwz	r1,THREAD_INFO-THREAD(r1); /* this thread's kernel stack   */\
-	addi	r1,r1,THREAD_SIZE;					     \
+	ALLOC_STACK_FRAME(r1, THREAD_SIZE);				     \
 1:	subi	r1,r1,INT_FRAME_SIZE;	/* Allocate an exception frame     */\
 	mr	r11,r1;							     \
 	stw	r10,_CCR(r11);          /* save various registers	   */\
diff --git a/arch/powerpc/platforms/44x/Kconfig b/arch/powerpc/platforms/44x/Kconfig
index 3496bc0..346b293 100644
--- a/arch/powerpc/platforms/44x/Kconfig
+++ b/arch/powerpc/platforms/44x/Kconfig
@@ -214,6 +214,16 @@  config 440SPe
 	bool
 	select IBM_NEW_EMAC_EMAC4
 
+config STDBINUTILS
+	bool "Using standard binutils"
+	depends on 44x
+	default y
+	help
+	  Turning this option off allows you to select 256KB PAGE_SIZE on 44x.
+	  Note, that kernel will be able to run only those applications,
+	  which had been compiled using the patched binutils (ELF standard
+	  supports only page sizes up to 64K).
+
 config 460EX
 	bool
 	select PPC_FPU