[PATCH 1/2] iommu/arm-smmu-v3: Do not bother impl_ops if IOMMU_VIOMMU_TYPE_ARM_SMMUV3

[Nicolin Chen]

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 missing a pairing impl's
vsmmu_init should be a driver bug too. Warn these two cases.

Suggested-by: Will Deacon <will at kernel.org>
Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
---
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     | 30 ++++++++++++-------
 1 file changed, 19 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..0b2acb80f41b 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 +446,21 @@ 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;
+	/*
+	 * If a non standard type was supported in arm_smmu_get_viommu_size() by
+	 * an implementation, a pairing vsmmu_init op must exist.
+	 */
+	if (WARN_ON_ONCE(!smmu->impl_ops || !smmu->impl_ops->vsmmu_init))
+		return -EOPNOTSUPP;
+	/* 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)
-- 
2.43.0