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

Baolu Lu
2023-03-10T02:12:08Z

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