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

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@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com Signed-off-by: Yi Liu yi.l.liu@intel.com

---

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