On Fri, Aug 30, 2024 at 03:27:00PM +0000, Mostafa Saleh wrote:

Hi Jason,

On Tue, Aug 27, 2024 at 12:51:37PM -0300, Jason Gunthorpe wrote:

quoted

For SMMUv3 the parent must be a S2 domain, which can be composed
into a IOMMU_DOMAIN_NESTED.

In future the S2 parent will also need a VMID linked to the VIOMMU and
even to KVM.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

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 ec2fcdd4523a26..8db3db6328f8b7 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -3103,7 +3103,8 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
 			   const struct iommu_user_data *user_data)
 {
 	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
-	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
+	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
+				 IOMMU_HWPT_ALLOC_NEST_PARENT;
 	struct arm_smmu_domain *smmu_domain;
 	int ret;
 

@@ -3116,6 +3117,14 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
 	if (!smmu_domain)
 		return ERR_PTR(-ENOMEM);
 
+	if (flags & IOMMU_HWPT_ALLOC_NEST_PARENT) {
+		if (!(master->smmu->features & ARM_SMMU_FEAT_NESTING)) {
+			ret = -EOPNOTSUPP;

I think that should be:
	ret = ERR_PTR(-EOPNOTSUPP);

Read again :)

static struct iommu_domain *
arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
			   struct iommu_domain *parent,
			   const struct iommu_user_data *user_data)
{
	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
				 IOMMU_HWPT_ALLOC_NEST_PARENT;
	struct arm_smmu_domain *smmu_domain;
	int ret;
     ^^^^^^^^^^^^^^

err_free:
	kfree(smmu_domain);
	return ERR_PTR(ret);
           ^^^^^^^^^^^^^^^^^^

Jason