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ARC: mm: Introduce explicit super page size support 

MMUv4 supports 2 concurrent page sizes: Normal and Super [4K to 16M]

So far Linux supported a single super page size for a given Normal page,
depending on the software page walking address split.
e.g. we had 11:8:13 address split for 8K page, which meant super page
was 2 ^(8+13) = 2M (given that THP size has to be PMD_SHIFT)

Now we turn this around, by allowing multiple Super Pages in Kconfig
(currently 2M and 16M only) and forcing page walker address split to
PGDIR_SHIFT and PAGE_SHIFT

For configs without Super page, things are same as before and
PGDIR_SHIFT can be hacked to get non default address split

The motivation for this change is a customer who needs 16M super page
and a 8K Normal page combo.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2016-02-10 06:52:07 +05:30
parent dec2b2849c
commit 37eda9df5b
2 changed files with 45 additions and 19 deletions
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19
arch/arc/Kconfig
View File

@ -341,6 +341,19 @@ config ARC_PAGE_SIZE_4K
endchoice
choice
prompt "MMU Super Page Size"
depends on ISA_ARCV2 && TRANSPARENT_HUGEPAGE
default ARC_HUGEPAGE_2M
config ARC_HUGEPAGE_2M
bool "2MB"
config ARC_HUGEPAGE_16M
bool "16MB"
endchoice
if ISA_ARCOMPACT
config ARC_COMPACT_IRQ_LEVELS
@ -569,6 +582,12 @@ endmenu
endmenu # "ARC Architecture Configuration"
source "mm/Kconfig"
config FORCE_MAX_ZONEORDER
int "Maximum zone order"
default "12" if ARC_HUGEPAGE_16M
default "11"
source "net/Kconfig"
source "drivers/Kconfig"
source "fs/Kconfig"

45
arch/arc/include/asm/pgtable.h
View File

@ -179,37 +179,44 @@
#define __S111 PAGE_U_X_W_R
/****************************************************************
* Page Table Lookup split
* 2 tier (PGD:PTE) software page walker
*
* We implement 2 tier paging and since this is all software, we are free
* to customize the span of a PGD / PTE entry to suit us
*
* 32 bit virtual address
* [31] 32 bit virtual address [0]
* -------------------------------------------------------
* | BITS_FOR_PGD | BITS_FOR_PTE | BITS_IN_PAGE |
* | | <------------ PGDIR_SHIFT ----------> |
* | | |
* | BITS_FOR_PGD | BITS_FOR_PTE | <-- PAGE_SHIFT --> |
* -------------------------------------------------------
* | | |
* | | --> off in page frame
* | |
* | ---> index into Page Table
* |
* ----> index into Page Directory
*
* In a single page size configuration, only PAGE_SHIFT is fixed
* So both PGD and PTE sizing can be tweaked
* e.g. 8K page (PAGE_SHIFT 13) can have
* - PGDIR_SHIFT 21 -> 11:8:13 address split
* - PGDIR_SHIFT 24 -> 8:11:13 address split
*
* If Super Page is configured, PGDIR_SHIFT becomes fixed too,
* so the sizing flexibility is gone.
*/
#define BITS_IN_PAGE PAGE_SHIFT
/* Optimal Sizing of Pg Tbl - based on MMU page size */
#if defined(CONFIG_ARC_PAGE_SIZE_8K)
#define BITS_FOR_PTE 8 /* 11:8:13 */
#elif defined(CONFIG_ARC_PAGE_SIZE_16K)
#define BITS_FOR_PTE 8 /* 10:8:14 */
#elif defined(CONFIG_ARC_PAGE_SIZE_4K)
#define BITS_FOR_PTE 9 /* 11:9:12 */
#if defined(CONFIG_ARC_HUGEPAGE_16M)
#define PGDIR_SHIFT 24
#elif defined(CONFIG_ARC_HUGEPAGE_2M)
#define PGDIR_SHIFT 21
#else
/*
* Only Normal page support so "hackable" (see comment above)
* Default value provides 11:8:13 (8K), 11:9:12 (4K)
*/
#define PGDIR_SHIFT 21
#endif
#define BITS_FOR_PGD (32 - BITS_FOR_PTE - BITS_IN_PAGE)
#define BITS_FOR_PTE (PGDIR_SHIFT - PAGE_SHIFT)
#define BITS_FOR_PGD (32 - PGDIR_SHIFT)
#define PGDIR_SHIFT (32 - BITS_FOR_PGD)
#define PGDIR_SIZE (1UL << PGDIR_SHIFT) /* vaddr span, not PDG sz */
#define PGDIR_MASK (~(PGDIR_SIZE-1))