linux-kernel - [PATCH 1/3] iommu/arm-smmu: Don't blindly use first SMR to calculate mask

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Date:   Thu, 26 Dec 2019 14:17:07 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Patrick Daly <pdaly@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Rob Clark <robdclark@...il.com>
Subject: [PATCH 1/3] iommu/arm-smmu: Don't blindly use first SMR to calculate mask

With the SMRs inherited from the bootloader the first SMR might actually
be valid and in use. As such probing the SMR mask using the first SMR
might break a stream in use. Search for an unused stream and use this to
probe the SMR mask.

Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
---

Changes since RFC:
- Deal with EXIDS
- Use arm_smmu_gr0_read/write()

 drivers/iommu/arm-smmu.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 4f1a350d9529..6ca6a4e072c8 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -945,24 +945,43 @@ static void arm_smmu_write_sme(struct arm_smmu_device *smmu, int idx)
  */
 static void arm_smmu_test_smr_masks(struct arm_smmu_device *smmu)
 {
+	u32 s2cr;
 	u32 smr;
+	int idx;
 
 	if (!smmu->smrs)
 		return;
 
+	for (idx = 0; idx < smmu->num_mapping_groups; idx++) {
+		if (smmu->features & ARM_SMMU_FEAT_EXIDS) {
+			s2cr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_S2CR(idx));
+			if (!FIELD_GET(S2CR_EXIDVALID, s2cr))
+				break;
+		} else {
+			smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(idx));
+			if (!FIELD_GET(SMR_VALID, smr))
+				break;
+		}
+	}
+
+	if (idx == smmu->num_mapping_groups) {
+		dev_err(smmu->dev, "Unable to compute streamid_mask\n");
+		return;
+	}
+
 	/*
 	 * SMR.ID bits may not be preserved if the corresponding MASK
 	 * bits are set, so check each one separately. We can reject
 	 * masters later if they try to claim IDs outside these masks.
 	 */
 	smr = FIELD_PREP(SMR_ID, smmu->streamid_mask);
-	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(0), smr);
-	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(0));
+	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(idx), smr);
+	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(idx));
 	smmu->streamid_mask = FIELD_GET(SMR_ID, smr);
 
 	smr = FIELD_PREP(SMR_MASK, smmu->streamid_mask);
-	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(0), smr);
-	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(0));
+	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(idx), smr);
+	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(idx));
 	smmu->smr_mask_mask = FIELD_GET(SMR_MASK, smr);
 }
 
-- 
2.24.0