linux-kernel - [PATCH 3.2 098/200] ARM: 7953/1: mm: ensure TLB invalidation is complete before enabling MMU

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Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Will Deacon" <will.deacon@....com>,
	"Russell King" <rmk+kernel@....linux.org.uk>,
	"Albin Tonnerre" <Albin.Tonnerre@....com>
Subject: [PATCH 3.2 098/200] ARM: 7953/1: mm: ensure TLB invalidation is
 complete before enabling MMU

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.deacon@....com>

commit bae0ca2bc550d1ec6a118fb8f2696f18c4da3d8e upstream.

During __v{6,7}_setup, we invalidate the TLBs since we are about to
enable the MMU on return to head.S. Unfortunately, without a subsequent
dsb instruction, the invalidation is not guaranteed to have completed by
the time we write to the sctlr, potentially exposing us to junk/stale
translations cached in the TLB.

This patch reworks the init functions so that the dsb used to ensure
completion of cache/predictor maintenance is also used to ensure
completion of the TLB invalidation.

Reported-by: Albin Tonnerre <Albin.Tonnerre@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/mm/proc-v6.S | 3 ++-
 arch/arm/mm/proc-v7.S | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -199,7 +199,6 @@ __v6_setup:
 	mcr	p15, 0, r0, c7, c14, 0		@ clean+invalidate D cache
 	mcr	p15, 0, r0, c7, c5, 0		@ invalidate I cache
 	mcr	p15, 0, r0, c7, c15, 0		@ clean+invalidate cache
-	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer
 #ifdef CONFIG_MMU
 	mcr	p15, 0, r0, c8, c7, 0		@ invalidate I + D TLBs
 	mcr	p15, 0, r0, c2, c0, 2		@ TTB control register
@@ -209,6 +208,8 @@ __v6_setup:
 	ALT_UP(orr	r8, r8, #TTB_FLAGS_UP)
 	mcr	p15, 0, r8, c2, c0, 1		@ load TTB1
 #endif /* CONFIG_MMU */
+	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer and
+						@ complete invalidations
 	adr	r5, v6_crval
 	ldmia	r5, {r5, r6}
 #ifdef CONFIG_CPU_ENDIAN_BE8
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -368,7 +368,6 @@ __v7_setup:
 
 3:	mov	r10, #0
 	mcr	p15, 0, r10, c7, c5, 0		@ I+BTB cache invalidate
-	dsb
 #ifdef CONFIG_MMU
 	mcr	p15, 0, r10, c8, c7, 0		@ invalidate I + D TLBs
 	mcr	p15, 0, r10, c2, c0, 2		@ TTB control register
@@ -382,6 +381,7 @@ __v7_setup:
 	mcr	p15, 0, r5, c10, c2, 0		@ write PRRR
 	mcr	p15, 0, r6, c10, c2, 1		@ write NMRR
 #endif
+	dsb					@ Complete invalidations
 #ifndef CONFIG_ARM_THUMBEE
 	mrc	p15, 0, r0, c0, c1, 0		@ read ID_PFR0 for ThumbEE
 	and	r0, r0, #(0xf << 12)		@ ThumbEE enabled field

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