From: Jean-Philippe Brucker <jean-philippe@linaro.org>
Date: Mon, 24 Feb 2020 17:58:43 +0100
Subject: iommu/arm-smmu-v3: Write level-1 descriptors atomically
Git-commit: 87e5fe5b779a20fa02382aaf169015e68710b9ff
Patch-mainline: v5.7-rc1
References: bsc#1175713

Use WRITE_ONCE() to make sure that the SMMU doesn't read incomplete
stream table descriptors. Refer to the comment about 64-bit accesses,
and add the comment to the equivalent context descriptor code.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/arm-smmu-v3.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 6b76df37025e..068a16d0eabe 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1531,6 +1531,7 @@ static void arm_smmu_write_cd_l1_desc(__le64 *dst,
 	u64 val = (l1_desc->l2ptr_dma & CTXDESC_L1_DESC_L2PTR_MASK) |
 		  CTXDESC_L1_DESC_V;
 
+	/* See comment in arm_smmu_write_ctx_desc() */
 	WRITE_ONCE(*dst, cpu_to_le64(val));
 }
 
@@ -1726,7 +1727,8 @@ arm_smmu_write_strtab_l1_desc(__le64 *dst, struct arm_smmu_strtab_l1_desc *desc)
 	val |= FIELD_PREP(STRTAB_L1_DESC_SPAN, desc->span);
 	val |= desc->l2ptr_dma & STRTAB_L1_DESC_L2PTR_MASK;
 
-	*dst = cpu_to_le64(val);
+	/* See comment in arm_smmu_write_ctx_desc() */
+	WRITE_ONCE(*dst, cpu_to_le64(val));
 }
 
 static void arm_smmu_sync_ste_for_sid(struct arm_smmu_device *smmu, u32 sid)