Re: [RFC PATCH v4 03/16] iommu/arm-smmu-v3: Add initial pSMMU realm viommu plumbing

[Aneesh Kumar K.V <aneesh.kumar@kernel.org>]

Jason Gunthorpe <jgg@ziepe.ca> writes:

> On Tue, Sep 01, 2026 at 03:36:37PM +0530, Aneesh Kumar K.V wrote:
>
>> @@ -463,14 +460,13 @@
>>  	vsmmu->vmid = s2_parent->s2_cfg.vmid;
>>  
>>  	if (viommu->type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3) {
>> +		if (arm_smmu_is_realm_viommu(viommu))
>> +			return arm_realm_smmu_v3_init(viommu, user_data);
>> +
>
> I think the realm vsmmu is going to require a different info struct
> than the normal psmmu case, isn't it?
>
> If so it needs its own enum value.
>
> It would be nice to see a draft patch showing how the real vsmmu works
> on top of the RMM spec for it. If we are using a viommu object then
> non-vsmmu case should be identical just with an option in the info
> struct to not create the vsmmu object.
>

Based on feedback on other emails in this thread, I have now implemented
this without using a vdevice or viommu. This should make the CCA and
non-CCA cases similar.

This ends up adding:

modified   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4324,6 +4324,8 @@ static const struct iommu_ops arm_smmu_ops = {
 	.def_domain_type	= arm_smmu_def_domain_type,
 	.get_viommu_size	= arm_smmu_get_viommu_size,
 	.viommu_init		= arm_vsmmu_init,
+	.tsm_bind		= arm_smmu_realm_tsm_bind,
+	.tsm_unbind		= arm_smmu_realm_tsm_unbind,
 	.user_pasid_table	= 1,
 	.owner			= THIS_MODULE,
 	.default_domain_ops = &(const struct iommu_domain_ops) {


and

+int arm_smmu_realm_tsm_bind(struct device *dev, struct kvm *kvm)
+{
+	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+	int ret;
+
+	if (!kvm_is_realm(kvm))
+		return 0;
+
+	ret = arm_realm_smmu_get(master->smmu);
+	if (ret)
+		return ret;
+
+	ret = arm_realm_smmu_stream_get(master);
+	if (ret)
+		arm_realm_smmu_put(master->smmu);
+	return ret;
+}
+
+void arm_smmu_realm_tsm_unbind(struct device *dev, struct kvm *kvm)
+{
+	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+
+	if (!kvm_is_realm(kvm))
+		return;
+
+	arm_realm_smmu_stream_put(master);
+	arm_realm_smmu_put(master->smmu);
+}

and tsm op iotcl now becomes

iommufd_device_tsm_op_ioctl()

	switch (cmd->type) {
	case IOMMU_DEVICE_TSM_BIND:
		if (!idev->tsm_iommu_bound && ops->tsm_bind) {
			if (WARN_ON_ONCE(!ops->tsm_unbind)) {
				ret = -EOPNOTSUPP;
				break;
			}
			ret = ops->tsm_bind(idev->dev, kvm);
			if (ret)
				break;
			idev->tsm_iommu_bound = true;
			iommu_bound = true;
		}
		ret = tsm_bind(idev->dev, kvm, cmd->tdi_id);
		if (ret && iommu_bound) {
			ops->tsm_unbind(idev->dev, kvm);
			idev->tsm_iommu_bound = false;
		}
		break;
	case IOMMU_DEVICE_TSM_UNBIND:
		__iommufd_device_tsm_unbind(idev);
		ret = 0;
		break;
	default:
		ret = -EINVAL;
		break;
	}

I am yet to clean up the changes. I just wanted to share that we can
possibly drop the vdevice/viommu requirement.

-aneesh