On 8/15/21 2:27 AM, Mike Rapoport wrote:
On Thu, Aug 12, 2021 at 04:37:50PM -0700, Vineet Gupta wrote:
ARCv2 MMU is software walked and Linux implements 2 levels of paging: pgd/pte.
Forthcoming hw will have multiple levels, so this change preps mm code
for same. It is also fun to try multi levels even on soft-walked code to
ensure generic mm code is robust to handle.
overview
________
2 levels {pgd, pte} : pmd is folded but pmd_* macros are valid and operate on pgd
3 levels {pgd, pmd, pte}:
- pud is folded and pud_* macros point to pgd
- pmd_* macros operate on actual pmd
code changes
____________
1. #include <asm-generic/pgtable-nopud.h>
2. Define CONFIG_PGTABLE_LEVELS 3
3a. Define PMD_SHIFT, PMD_SIZE, PMD_MASK, pmd_t
3b. Define pmd_val() which actually deals with pmd
(pmd_offset(), pmd_index() are provided by generic code)
3c. pmd_alloc_one()/pmd_free() also provided by generic code
(pmd_populate/pmd_free already exist)
4. Define pud_none(), pud_bad() macros based on generic pud_val() which
internally pertains to pgd now.
4b. define pud_populate() to just setup pgd
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxx>
---
...
diff --git a/arch/arc/include/asm/pgtable-levels.h b/arch/arc/include/asm/pgtable-levels.h
index 8ece75335bb5..1c2f022d4ad0 100644
--- a/arch/arc/include/asm/pgtable-levels.h
+++ b/arch/arc/include/asm/pgtable-levels.h
@@ -10,6 +10,8 @@
#ifndef _ASM_ARC_PGTABLE_LEVELS_H
#define _ASM_ARC_PGTABLE_LEVELS_H
+#if CONFIG_PGTABLE_LEVELS == 2
+
/*
* 2 level paging setup for software walked MMUv3 (ARC700) and MMUv4 (HS)
*
@@ -37,16 +39,38 @@
#define PGDIR_SHIFT 21
#endif
-#define PGDIR_SIZE BIT(PGDIR_SHIFT) /* vaddr span, not PDG sz */
-#define PGDIR_MASK (~(PGDIR_SIZE - 1))
+#else
Adding /* CONFIG_PGTABLE_LEVELS == 2 */ would make the whole thing a bit
more readable, I think.
You meant
+#else /* CONFIG_PGTABLE_LEVELS != 2
+
+/*
+ * A default 3 level paging testing setup in software walked MMU
+ * MMUv4 (8K page): <4> : <7> : <8> : <13>
+ */
+#define PGDIR_SHIFT 28
+#if CONFIG_PGTABLE_LEVELS > 2
+#define PMD_SHIFT 21
+#endif
+
+#endif
and here as well.
I added following to indicate conditional coding for levels related code
+#endif /* CONFIG_PGTABLE_LEVELS */
+#define PGDIR_SIZE BIT(PGDIR_SHIFT)
+#define PGDIR_MASK (~(PGDIR_SIZE - 1))
#define PTRS_PER_PGD BIT(32 - PGDIR_SHIFT)
-#define PTRS_PER_PTE BIT(PGDIR_SHIFT - PAGE_SHIFT)
+#if CONFIG_PGTABLE_LEVELS > 2
+#define PMD_SIZE BIT(PMD_SHIFT)
+#define PMD_MASK (~(PMD_SIZE - 1))
+#define PTRS_PER_PMD BIT(PGDIR_SHIFT - PMD_SHIFT)
+#endif
+
+#define PTRS_PER_PTE BIT(PMD_SHIFT - PAGE_SHIFT)
