linux-kernel - [PATCH 4.4 09/56] iommu/arm-smmu-v3: Clear prior settings when updating STEs

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Date:   Mon, 13 Nov 2017 13:55:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nate Watterson <nwatters@...eaurora.org>,
        Will Deacon <will.deacon@....com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.4 09/56] iommu/arm-smmu-v3: Clear prior settings when updating STEs

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Nate Watterson <nwatters@...eaurora.org>


[ Upstream commit 810871c57011eb3e89e6768932757f169d666cd2 ]

To prevent corruption of the stage-1 context pointer field when
updating STEs, rebuild the entire containing dword instead of
clearing individual fields.

Signed-off-by: Nate Watterson <nwatters@...eaurora.org>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/iommu/arm-smmu-v3.c |   10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1033,13 +1033,8 @@ static void arm_smmu_write_strtab_ent(st
 		}
 	}
 
-	/* Nuke the existing Config, as we're going to rewrite it */
-	val &= ~(STRTAB_STE_0_CFG_MASK << STRTAB_STE_0_CFG_SHIFT);
-
-	if (ste->valid)
-		val |= STRTAB_STE_0_V;
-	else
-		val &= ~STRTAB_STE_0_V;
+	/* Nuke the existing STE_0 value, as we're going to rewrite it */
+	val = ste->valid ? STRTAB_STE_0_V : 0;
 
 	if (ste->bypass) {
 		val |= disable_bypass ? STRTAB_STE_0_CFG_ABORT
@@ -1068,7 +1063,6 @@ static void arm_smmu_write_strtab_ent(st
 		val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK
 		        << STRTAB_STE_0_S1CTXPTR_SHIFT) |
 			STRTAB_STE_0_CFG_S1_TRANS;
-
 	}
 
 	if (ste->s2_cfg) {