[PATCH] iommu/arm-smmu-v3: Ensure we sync STE when only changing config field

[will.deacon@arm.com (Will Deacon)]

The SMMUv3 architecture permits caching of data structures deemed to be
"reachable" by the SMU, which includes STEs marked as invalid. When
transitioning an STE to a bypass/fault configuration at init or detach
time, we mistakenly elide the CMDQ_OP_CFGI_STE operation in some cases,
therefore potentially leaving the old STE state cached in the SMMU.

This patch fixes the problem by ensuring that we perform the
CMDQ_OP_CFGI_STE operation irrespective of the validity of the previous
STE.

Cc: Robin Murphy <robin.murphy@arm.com>
Reported-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 drivers/iommu/arm-smmu-v3.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 47f52b1ab838..91fdabdb4de6 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1085,8 +1085,11 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
 		dst[1] = cpu_to_le64(STRTAB_STE_1_SHCFG_INCOMING
 			 << STRTAB_STE_1_SHCFG_SHIFT);
 		dst[2] = 0; /* Nuke the VMID */
-		if (ste_live)
-			arm_smmu_sync_ste_for_sid(smmu, sid);
+		/*
+		 * The SMMU can perform negative caching, so we must sync
+		 * the STE regardless of whether the old value was live.
+		 */
+		arm_smmu_sync_ste_for_sid(smmu, sid);
 		return;
 	}
 
-- 
2.1.4