[PATCH 11/17] iommufd: Add infrastructure for user-managed hw_pagetable allocation

[Yi Liu <yi.l.liu@xxxxxxxxx>]

Nested translation has stage-1 and stage-2 hw_pagetables, and both needs
userspace to allocate. Stage-1 hw_pagetable needs to work with a stage-2
hw_pagetable. This adds a parent pointer in struct iommufd_hw_pagetable
to link stage-1 hw_pagetable with a stage-2 hw_pagetable. Hence iommufd
core can accept user-managed hw_pagetable allocation request.

Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
 drivers/iommu/iommufd/device.c          |  5 +++++
 drivers/iommu/iommufd/hw_pagetable.c    | 21 +++++++++++++++------
 drivers/iommu/iommufd/iommufd_private.h |  1 +
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index cdc4ab36f52d..6d948fa418d5 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -301,6 +301,9 @@ static int iommufd_device_attach_ioas(struct iommufd_device *idev,
 	struct io_pagetable *iopt;
 	int rc;
 
+	if (hwpt->parent)
+		hwpt = hwpt->parent;
+
 	iopt = &hwpt->ioas->iopt;
 
 	rc = iopt_table_enforce_group_resv_regions(iopt, idev->dev,
@@ -321,6 +324,8 @@ static int iommufd_device_attach_ioas(struct iommufd_device *idev,
 static void iommufd_device_detach_ioas(struct iommufd_device *idev,
 				       struct iommufd_hw_pagetable *hwpt)
 {
+	if (hwpt->parent)
+		hwpt = hwpt->parent;
 	iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->dev);
 }
 
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index 998d01490a74..02dee8e8d958 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -15,8 +15,12 @@ void iommufd_hw_pagetable_destroy(struct iommufd_object *obj)
 
 	WARN_ON(!list_empty(&hwpt->devices));
 
-	iopt_table_remove_domain(&hwpt->ioas->iopt, hwpt->domain);
-	list_del(&hwpt->hwpt_item);
+	if (!hwpt->parent) {
+		iopt_table_remove_domain(&hwpt->ioas->iopt, hwpt->domain);
+		list_del(&hwpt->hwpt_item);
+	} else {
+		refcount_dec(&hwpt->parent->obj.users);
+	}
 	iommu_domain_free(hwpt->domain);
 	refcount_dec(&hwpt->ioas->obj.users);
 	mutex_destroy(&hwpt->devices_lock);
@@ -58,13 +62,18 @@ __iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx,
 		goto out_abort;
 	}
 
+	hwpt->parent = parent;
 	INIT_LIST_HEAD(&hwpt->devices);
 	INIT_LIST_HEAD(&hwpt->hwpt_item);
 	mutex_init(&hwpt->devices_lock);
-	rc = iopt_table_add_domain(&ioas->iopt, hwpt->domain);
-	if (rc)
-		goto out_free_domain;
-	list_add_tail(&hwpt->hwpt_item, &ioas->hwpt_list);
+	if (!parent) {
+		rc = iopt_table_add_domain(&ioas->iopt, hwpt->domain);
+		if (rc)
+			goto out_free_domain;
+		list_add_tail(&hwpt->hwpt_item, &ioas->hwpt_list);
+	} else {
+		refcount_inc(&parent->obj.users);
+	}
 
 	/* Pairs with iommufd_hw_pagetable_destroy() */
 	refcount_inc(&ioas->obj.users);
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index ee5344baf135..5ef034451f4b 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -241,6 +241,7 @@ int iommufd_vfio_ioas(struct iommufd_ucmd *ucmd);
  */
 struct iommufd_hw_pagetable {
 	struct iommufd_object obj;
+	struct iommufd_hw_pagetable *parent;
 	struct iommufd_ioas *ioas;
 	struct iommu_domain *domain;
 	bool auto_domain : 1;
-- 
2.34.1