linux-kernel - [PATCH v2 6.1 3/4] iommu/arm-smmu-v3: Add explicit feature for nesting

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Date:   Wed,  2 Aug 2023 17:09:10 +0000
From:   Easwar Hariharan <eahariha@...ux.microsoft.com>
To:     stable@...r.kernel.org
Cc:     easwar.hariharan@...rosoft.com,
        Robin Murphy <robin.murphy@....com>,
        Nicolin Chen <nicolinc@...dia.com>,
        Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Sasha Levin <sashal@...nel.org>,
        Yicong Yang <yangyicong@...ilicon.com>,
        Tomas Krcka <krckatom@...zon.de>,
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM SMMU DRIVERS),
        iommu@...ts.linux-foundation.org (open list:IOMMU DRIVERS),
        iommu@...ts.linux.dev (open list:IOMMU DRIVERS),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 6.1 3/4] iommu/arm-smmu-v3: Add explicit feature for nesting

From: Robin Murphy <robin.murphy@....com>

commit 1d9777b9f3d55b4b6faf186ba4f1d6fb560c0523 upstream

In certain cases we may want to refuse to allow nested translation even
when both stages are implemented, so let's add an explicit feature for
nesting support which we can control in its own right. For now this
merely serves as documentation, but it means a nice convenient check
will be ready and waiting for the future nesting code.

Signed-off-by: Robin Murphy <robin.murphy@....com>
Reviewed-by: Nicolin Chen <nicolinc@...dia.com>
Link: https://lore.kernel.org/r/136c3f4a3a84cc14a5a1978ace57dfd3ed67b688.1683731256.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Easwar Hariharan <eahariha@...ux.microsoft.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 ++++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 6a551a48d271..7cec4a457d91 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3703,6 +3703,10 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 
 	smmu->ias = max(smmu->ias, smmu->oas);
 
+	if ((smmu->features & ARM_SMMU_FEAT_TRANS_S1) &&
+	    (smmu->features & ARM_SMMU_FEAT_TRANS_S2))
+		smmu->features |= ARM_SMMU_FEAT_NESTING;
+
 	arm_smmu_device_iidr_probe(smmu);
 
 	if (arm_smmu_sva_supported(smmu))
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index abaecdf8d5d2..c594a9b46999 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -646,6 +646,7 @@ struct arm_smmu_device {
 #define ARM_SMMU_FEAT_BTM		(1 << 16)
 #define ARM_SMMU_FEAT_SVA		(1 << 17)
 #define ARM_SMMU_FEAT_E2H		(1 << 18)
+#define ARM_SMMU_FEAT_NESTING		(1 << 19)
 	u32				features;
 
 #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
-- 
2.25.1