[PATCH v4 04/11] iommufd/viommu: Add IOMMU_VIOMMU_ALLOC ioctl

[Tian, Kevin]

> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: Tuesday, October 22, 2024 8:19 AM
> 
> Add a new ioctl for user space to do a vIOMMU allocation. It must be based
> on a nesting parent HWPT, so take its refcount.
> 
> If an IOMMU driver supports a driver-managed vIOMMU object, it must
> define

why highlight 'driver-managed', implying a core-managed vIOMMU 
object some day?

> +/**
> + * struct iommu_viommu_alloc - ioctl(IOMMU_VIOMMU_ALLOC)
> + * @size: sizeof(struct iommu_viommu_alloc)
> + * @flags: Must be 0
> + * @type: Type of the virtual IOMMU. Must be defined in enum
> iommu_viommu_type
> + * @dev_id: The device's physical IOMMU will be used to back the virtual
> IOMMU
> + * @hwpt_id: ID of a nesting parent HWPT to associate to
> + * @out_viommu_id: Output virtual IOMMU ID for the allocated object
> + *
> + * Allocate a virtual IOMMU object that represents the underlying physical
> + * IOMMU's virtualization support. The vIOMMU object is a security-isolated
> + * slice of the physical IOMMU HW that is unique to a specific VM.

the object itself is a software abstraction, while a 'slice' is a set of
real hw resources.