linux-kernel - [PATCH v3 1/2] iommu/arm-smmu-v3: Do not bother impl_ops if IOMMU_VIOMMU_TYPE_ARM

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Message-ID: <20250721200444.1740461-2-nicolinc@nvidia.com>
Date: Mon, 21 Jul 2025 13:04:43 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <jgg@...dia.com>, <will@...nel.org>
CC: <joro@...tes.org>, <robin.murphy@....com>,
	<linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>
Subject: [PATCH v3 1/2] iommu/arm-smmu-v3: Do not bother impl_ops if IOMMU_VIOMMU_TYPE_ARM_SMMUV3

When viommu type is IOMMU_VIOMMU_TYPE_ARM_SMMUV3, always return or init the
standard struct arm_vsmmu, instead of going through impl_ops that must have
its own viommu type than the standard IOMMU_VIOMMU_TYPE_ARM_SMMUV3.

Given that arm_vsmmu_init() is called after arm_smmu_get_viommu_size(), any
unsupported viommu->type must be a corruption. And it must be a driver bug
that its vsmmu_size and vsmmu_init ops aren't paired. Warn these two cases.

Suggested-by: Will Deacon <will@...nel.org>
Acked-by: Will Deacon <will@...nel.org>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     | 24 ++++++++++---------
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 14 +++++++++++
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
index d9bea8f1f636..c034d6c5468f 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
@@ -420,14 +420,13 @@ size_t arm_smmu_get_viommu_size(struct device *dev,
 	    !(smmu->features & ARM_SMMU_FEAT_S2FWB))
 		return 0;
 
-	if (smmu->impl_ops && smmu->impl_ops->vsmmu_size &&
-	    viommu_type == smmu->impl_ops->vsmmu_type)
-		return smmu->impl_ops->vsmmu_size;
+	if (viommu_type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3)
+		return VIOMMU_STRUCT_SIZE(struct arm_vsmmu, core);
 
-	if (viommu_type != IOMMU_VIOMMU_TYPE_ARM_SMMUV3)
+	if (!smmu->impl_ops || !smmu->impl_ops->vsmmu_size ||
+	    viommu_type != smmu->impl_ops->vsmmu_type)
 		return 0;
-
-	return VIOMMU_STRUCT_SIZE(struct arm_vsmmu, core);
+	return smmu->impl_ops->vsmmu_size;
 }
 
 int arm_vsmmu_init(struct iommufd_viommu *viommu,
@@ -447,12 +446,15 @@ int arm_vsmmu_init(struct iommufd_viommu *viommu,
 	/* FIXME Move VMID allocation from the S2 domain allocation to here */
 	vsmmu->vmid = s2_parent->s2_cfg.vmid;
 
-	if (smmu->impl_ops && smmu->impl_ops->vsmmu_init &&
-	    viommu->type == smmu->impl_ops->vsmmu_type)
-		return smmu->impl_ops->vsmmu_init(vsmmu, user_data);
+	if (viommu->type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3) {
+		viommu->ops = &arm_vsmmu_ops;
+		return 0;
+	}
 
-	viommu->ops = &arm_vsmmu_ops;
-	return 0;
+	/* Unsupported type was rejected in arm_smmu_get_viommu_size() */
+	if (WARN_ON(viommu->type != smmu->impl_ops->vsmmu_type))
+		return -EOPNOTSUPP;
+	return smmu->impl_ops->vsmmu_init(vsmmu, user_data);
 }
 
 int arm_vmaster_report_event(struct arm_smmu_vmaster *vmaster, u64 *evt)
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 181d07bc1a9d..9f4ad3705801 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4703,6 +4703,7 @@ static void arm_smmu_impl_remove(void *data)
 static struct arm_smmu_device *arm_smmu_impl_probe(struct arm_smmu_device *smmu)
 {
 	struct arm_smmu_device *new_smmu = ERR_PTR(-ENODEV);
+	const struct arm_smmu_impl_ops *ops;
 	int ret;
 
 	if (smmu->impl_dev && (smmu->options & ARM_SMMU_OPT_TEGRA241_CMDQV))
@@ -4713,11 +4714,24 @@ static struct arm_smmu_device *arm_smmu_impl_probe(struct arm_smmu_device *smmu)
 	if (IS_ERR(new_smmu))
 		return new_smmu;
 
+	ops = new_smmu->impl_ops;
+	if (ops) {
+		/* vsmmu_size and vsmmu_init ops must be paired */
+		if (WARN_ON(!ops->vsmmu_size != !ops->vsmmu_init)) {
+			ret = -EINVAL;
+			goto err_remove;
+		}
+	}
+
 	ret = devm_add_action_or_reset(new_smmu->dev, arm_smmu_impl_remove,
 				       new_smmu);
 	if (ret)
 		return ERR_PTR(ret);
 	return new_smmu;
+
+err_remove:
+	arm_smmu_impl_remove(new_smmu);
+	return ERR_PTR(ret);
 }
 
 static int arm_smmu_device_probe(struct platform_device *pdev)
-- 
2.43.0