ARM: 8109/1: mm: Modify pte_write and pmd_write logic for LPAE
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_AP2). 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@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
index 564f4b9..e4c8acf 100644
--- a/arch/arm/mm/proc-v7-3level.S
+++ b/arch/arm/mm/proc-v7-3level.S
@@ -87,8 +87,13 @@
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
