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authorVineet Gupta2016-02-10 06:52:07 +0530
committerVineet Gupta2016-02-12 12:10:25 +0530
commit37eda9df5bd8444263418495632ea6ec750f03f9 (patch)
tree2336e3a18d082fda05e907158b61fa34e2bcde7c
parentdec2b2849cfccf09822d6ce3f9bc84b8c8611152 (diff)
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>
-rw-r--r--arch/arc/Kconfig19
-rw-r--r--arch/arc/include/asm/pgtable.h45
2 files changed, 45 insertions, 19 deletions
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index bb15e8062b1f..63979c7eede5 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -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"
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 57af2f05ae84..d426d4215513 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -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))