[PATCH V5 2/2] arm: mm: Modify pte_write and pmd_write logic for LPAE
Steve Capper
steve.capper at linaro.org
Tue Jun 24 05:23:24 PDT 2014
For LPAE, we have the following means for encoding writable or dirty
ptes:
L_PTE_DIRTY L_PTE_RDONLY
!pte_dirty && !pte_write 0 1
!pte_dirty && pte_write 0 1
pte_dirty && !pte_write 1 1
pte_dirty && pte_write 1 0
So we can't distinguish between writeable clean ptes and read only
ptes. This can cause problems with ptes being incorrectly flagged as
read only when they are writeable but not dirty.
This patch renumbers L_PTE_RDONLY from AP[2] to a software bit #58,
and adds additional logic to set AP[2] whenever the pte is read only
or not dirty. That way we can distinguish between clean writeable ptes
and read only ptes.
HugeTLB pages will use this new logic automatically.
We need to add some logic to Transparent HugePages to ensure that they
correctly interpret the revised pgprot permissions (L_PTE_RDONLY has
moved and no longer matches PMD_SECT_RDONLY). In the process of
revising THP, the names of the PMD software bits have been prefixed
with L_ to make them easier to distinguish from their hardware bit
counterparts.
Signed-off-by: Steve Capper <steve.capper at linaro.org>
---
Changed in V5 -> rather than re-introduce L_PTE_WRITE we change
L_PTE_RDONLY to be a software bit #58. This allows us to leave the
two level code alone.
---
arch/arm/include/asm/pgtable-3level-hwdef.h | 1 +
arch/arm/include/asm/pgtable-3level.h | 37 +++++++++++++++++------------
arch/arm/mm/proc-v7-3level.S | 9 +++++--
3 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h
index 626989f..552a5f7 100644
--- a/arch/arm/include/asm/pgtable-3level-hwdef.h
+++ b/arch/arm/include/asm/pgtable-3level-hwdef.h
@@ -72,6 +72,7 @@
#define PTE_TABLE_BIT (_AT(pteval_t, 1) << 1)
#define PTE_BUFFERABLE (_AT(pteval_t, 1) << 2) /* AttrIndx[0] */
#define PTE_CACHEABLE (_AT(pteval_t, 1) << 3) /* AttrIndx[1] */
+#define PTE_AP2 (_AT(pteval_t, 1) << 7) /* AP[2] */
#define PTE_EXT_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */
#define PTE_EXT_AF (_AT(pteval_t, 1) << 10) /* Access Flag */
#define PTE_EXT_NG (_AT(pteval_t, 1) << 11) /* nG */
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index 3b10ec6..24ba2d7 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -79,18 +79,19 @@
#define L_PTE_PRESENT (_AT(pteval_t, 3) << 0) /* Present */
#define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */
#define L_PTE_USER (_AT(pteval_t, 1) << 6) /* AP[1] */
-#define L_PTE_RDONLY (_AT(pteval_t, 1) << 7) /* AP[2] */
#define L_PTE_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */
#define L_PTE_YOUNG (_AT(pteval_t, 1) << 10) /* AF */
#define L_PTE_XN (_AT(pteval_t, 1) << 54) /* XN */
#define L_PTE_DIRTY (_AT(pteval_t, 1) << 55) /* unused */
#define L_PTE_SPECIAL (_AT(pteval_t, 1) << 56) /* unused */
#define L_PTE_NONE (_AT(pteval_t, 1) << 57) /* PROT_NONE */
+#define L_PTE_RDONLY (_AT(pteval_t, 1) << 58) /* READ ONLY */
-#define PMD_SECT_VALID (_AT(pmdval_t, 1) << 0)
-#define PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55)
-#define PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56)
-#define PMD_SECT_NONE (_AT(pmdval_t, 1) << 57)
+#define L_PMD_SECT_VALID (_AT(pmdval_t, 1) << 0)
+#define L_PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55)
+#define L_PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56)
+#define L_PMD_SECT_NONE (_AT(pmdval_t, 1) << 57)
+#define L_PMD_SECT_RDONLY (_AT(pteval_t, 1) << 58)
/*
* To be used in assembly code with the upper page attributes.
@@ -214,24 +215,25 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
#define pmd_young(pmd) (pmd_isset((pmd), PMD_SECT_AF))
#define __HAVE_ARCH_PMD_WRITE
-#define pmd_write(pmd) (pmd_isclear((pmd), PMD_SECT_RDONLY))
+#define pmd_write(pmd) (pmd_isclear((pmd), L_PMD_SECT_RDONLY))
+#define pmd_dirty(pmd) (pmd_isset((pmd), L_PMD_SECT_DIRTY))
#define pmd_hugewillfault(pmd) (!pmd_young(pmd) || !pmd_write(pmd))
#define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd))
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define pmd_trans_huge(pmd) (pmd_val(pmd) && pmd_isclear((pmd), PMD_TABLE_BIT))
-#define pmd_trans_splitting(pmd) (pmd_isset((pmd), PMD_SECT_SPLITTING))
+#define pmd_trans_splitting(pmd) (pmd_isset((pmd), L_PMD_SECT_SPLITTING))
#endif
#define PMD_BIT_FUNC(fn,op) \
static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; }
-PMD_BIT_FUNC(wrprotect, |= PMD_SECT_RDONLY);
+PMD_BIT_FUNC(wrprotect, |= L_PMD_SECT_RDONLY);
PMD_BIT_FUNC(mkold, &= ~PMD_SECT_AF);
-PMD_BIT_FUNC(mksplitting, |= PMD_SECT_SPLITTING);
-PMD_BIT_FUNC(mkwrite, &= ~PMD_SECT_RDONLY);
-PMD_BIT_FUNC(mkdirty, |= PMD_SECT_DIRTY);
+PMD_BIT_FUNC(mksplitting, |= L_PMD_SECT_SPLITTING);
+PMD_BIT_FUNC(mkwrite, &= ~L_PMD_SECT_RDONLY);
+PMD_BIT_FUNC(mkdirty, |= L_PMD_SECT_DIRTY);
PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF);
#define pmd_mkhuge(pmd) (__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT))
@@ -245,8 +247,8 @@ PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF);
static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
{
- const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | PMD_SECT_RDONLY |
- PMD_SECT_VALID | PMD_SECT_NONE;
+ const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | L_PMD_SECT_RDONLY |
+ L_PMD_SECT_VALID | L_PMD_SECT_NONE;
pmd_val(pmd) = (pmd_val(pmd) & ~mask) | (pgprot_val(newprot) & mask);
return pmd;
}
@@ -257,8 +259,13 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
BUG_ON(addr >= TASK_SIZE);
/* create a faulting entry if PROT_NONE protected */
- if (pmd_val(pmd) & PMD_SECT_NONE)
- pmd_val(pmd) &= ~PMD_SECT_VALID;
+ if (pmd_val(pmd) & L_PMD_SECT_NONE)
+ pmd_val(pmd) &= ~L_PMD_SECT_VALID;
+
+ if (pmd_write(pmd) && pmd_dirty(pmd))
+ pmd_val(pmd) &= ~PMD_SECT_RDONLY;
+ else
+ pmd_val(pmd) |= PMD_SECT_RDONLY;
*pmdp = __pmd(pmd_val(pmd) | PMD_SECT_nG);
flush_pmd_entry(pmdp);
diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
index 22e3ad6..eb81123 100644
--- a/arch/arm/mm/proc-v7-3level.S
+++ b/arch/arm/mm/proc-v7-3level.S
@@ -86,8 +86,13 @@ ENTRY(cpu_v7_set_pte_ext)
tst rh, #1 << (57 - 32) @ L_PTE_NONE
bicne rl, #L_PTE_VALID
bne 1f
- tst rh, #1 << (55 - 32) @ L_PTE_DIRTY
- orreq rl, #L_PTE_RDONLY
+
+ eor ip, rh, #1 << (55 - 32) @ toggle L_PTE_DIRTY in temp reg to
+ @ test for !L_PTE_DIRTY || L_PTE_RDONLY
+ tst ip, #1 << (55 - 32) | 1 << (58 - 32)
+ orrne rl, #PTE_AP2
+ biceq rl, #PTE_AP2
+
1: strd r2, r3, [r0]
ALT_SMP(W(nop))
ALT_UP (mcr p15, 0, r0, c7, c10, 1) @ flush_pte
--
1.9.3
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