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Subject[PATCH v9 06/15] ARM: LPAE: add ISBs around MMU enabling code
Date
From: Will Deacon <will.deacon@arm.com>

Before we enable the MMU, we must ensure that the TTBR registers contain
sane values. After the MMU has been enabled, we jump to the *virtual*
address of the following function, so we also need to ensure that the
SCTLR write has taken effect.

This patch adds ISB instructions around the SCTLR write to ensure the
visibility of the above.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm/boot/compressed/head.S | 1 +
arch/arm/include/asm/assembler.h | 11 +++++++++++
arch/arm/kernel/head.S | 2 ++
arch/arm/kernel/sleep.S | 2 ++
4 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index c2effc9..c5d6025 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -659,6 +659,7 @@ __armv7_mmu_cache_on:
mcrne p15, 0, r3, c2, c0, 0 @ load page table pointer
mcrne p15, 0, r1, c3, c0, 0 @ load domain access control
#endif
+ mcr p15, 0, r0, c7, c5, 4 @ ISB
mcr p15, 0, r0, c1, c0, 0 @ load control register
mrc p15, 0, r0, c1, c0, 0 @ and read it back
mov r0, #0
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 29035e8..b6e65de 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -187,6 +187,17 @@
#endif

/*
+ * Instruction barrier
+ */
+ .macro instr_sync
+#if __LINUX_ARM_ARCH__ >= 7
+ isb
+#elif __LINUX_ARM_ARCH__ == 6
+ mcr p15, 0, r0, c7, c5, 4
+#endif
+ .endm
+
+/*
* SMP data memory barrier
*/
.macro smp_dmb mode
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 566c54c..6ee994c 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -400,8 +400,10 @@ ENDPROC(__enable_mmu)
.align 5
__turn_mmu_on:
mov r0, r0
+ instr_sync
mcr p15, 0, r0, c1, c0, 0 @ write control reg
mrc p15, 0, r3, c0, c0, 0 @ read id reg
+ instr_sync
mov r3, r3
mov r3, r13
mov pc, r3
diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
index 020e99c..4ac45fe 100644
--- a/arch/arm/kernel/sleep.S
+++ b/arch/arm/kernel/sleep.S
@@ -56,8 +56,10 @@ ENDPROC(cpu_suspend_abort)
.align 5
ENTRY(cpu_resume_mmu)
ldr r3, =cpu_resume_after_mmu
+ instr_sync
mcr p15, 0, r0, c1, c0, 0 @ turn on MMU, I-cache, etc
mrc p15, 0, r0, c0, c0, 0 @ read id reg
+ instr_sync
mov r0, r0
mov r0, r0
mov pc, r3 @ jump to virtual address


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