Re: [PATCH 04/12] iommufd: Pass parent hwpt and user_data to iommufd_hw_pagetable_alloc()

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On 3/9/23 4:09 PM, Yi Liu wrote:
Nested translation has stage-1 and stage-2 page tables. A stage-1 page
table is managed by user space, and it needs to work with a stage-2 page
table, which is a parent hwpt for the stage-1 hwpt.

iommu core already supports accepting parent iommu_domain and user_data
to allocate an iommu_domain. This makes iommufd_hw_pagetable_alloc() to
accept the parent hwpt and user_data, and relays them to iommu core, to
prepare for supporting hw_pagetable allocation with user_data.

Also, add a parent pointer in struct iommufd_hw_pagetable for taking and
releasing its refcount.

Co-developed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
  drivers/iommu/iommufd/device.c          |  2 +-
  drivers/iommu/iommufd/hw_pagetable.c    | 28 ++++++++++++++++++++++---
  drivers/iommu/iommufd/iommufd_private.h |  5 ++++-
  3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 5c352807d946..19cd6df46c6a 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -558,7 +558,7 @@ iommufd_device_auto_get_domain(struct iommufd_device *idev,
  	}
hwpt = iommufd_hw_pagetable_alloc(idev->ictx, ioas, idev,
-					  immediate_attach);
+					  NULL, NULL, immediate_attach);
  	if (IS_ERR(hwpt)) {
  		destroy_hwpt = ERR_CAST(hwpt);
  		goto out_unlock;
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index 84b4a11e62f8..16e92a1c150b 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -24,6 +24,8 @@ void iommufd_hw_pagetable_destroy(struct iommufd_object *obj)
  	if (hwpt->domain)
  		iommu_domain_free(hwpt->domain);
+ if (hwpt->parent)
+		refcount_dec(&hwpt->parent->obj.users);
  	refcount_dec(&hwpt->ioas->obj.users);
  }
@@ -46,6 +48,8 @@ int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt)
   * @ictx: iommufd context
   * @ioas: IOAS to associate the domain with
   * @idev: Device to get an iommu_domain for
+ * @parent: Optional parent HWPT to associate with the domain with
+ * @user_data: Optional user_data pointer
   * @immediate_attach: True if idev should be attached to the hwpt
   *
   * Allocate a new iommu_domain and return it as a hw_pagetable. The HWPT
@@ -54,14 +58,20 @@ int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt)
   */
  struct iommufd_hw_pagetable *
  iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
-			   struct iommufd_device *idev, bool immediate_attach)
+			   struct iommufd_device *idev,
+			   struct iommufd_hw_pagetable *parent,
+			   void *user_data, bool immediate_attach)
  {
  	const struct iommu_ops *ops = dev_iommu_ops(idev->dev);
+	struct iommu_domain *parent_domain = NULL;
  	struct iommufd_hw_pagetable *hwpt;
  	int rc;
lockdep_assert_held(&ioas->mutex); + if (parent && !ops->domain_alloc_user)
+		return ERR_PTR(-EOPNOTSUPP);

My understanding here is that we are checking whether domain_alloc_user
is required. It seems that as long as the caller inputs a valid
user_data or parent, domain_alloc_user is required. If so,

	if ((user_data || parent) && !ops->domain_alloc_user)
		return ERR_PTR(-EOPNOTSUPP);

Best regards,
baolu



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