Commit 37eda9df authored by Vineet Gupta's avatar Vineet Gupta
Browse files

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: default avatarVineet Gupta <vgupta@synopsys.com>
parent dec2b284

arch/arc/Kconfig

+19 −0
Original line number Diff line number Diff line
@@ -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"

arch/arc/include/asm/pgtable.h

+26 −19
Original line number Diff line number Diff line
@@ -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))

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