Re: [PATCH v2 2/4] vfio/iommufd: Add properties and handlers to TYPE_HOST_IOMMU_DEVICE_IOMMUFD

[Nicolin Chen <nicolinc@nvidia.com>]

On Fri, May 30, 2025 at 05:35:10PM +0800, Zhenzhong Duan wrote:
> Enhance HostIOMMUDeviceIOMMUFD object with 3 new members, specific
> to the iommufd BE + 2 new class functions.
> 
> IOMMUFD BE includes IOMMUFD handle, devid and hwpt_id. IOMMUFD handle
> and devid are used to allocate/free ioas and hwpt. hwpt_id is used to
> re-attach IOMMUFD backed device to its default VFIO sub-system created
> hwpt, i.e., when vIOMMU is disabled by guest. These properties are
> initialized in hiod::realize() after attachment.
>
> 2 new class functions are [at|de]tach_hwpt(). They are used to
> attach/detach hwpt. VFIO and VDPA can have different implementions,
> so implementation will be in sub-class instead of HostIOMMUDeviceIOMMUFD,
> e.g., in HostIOMMUDeviceIOMMUFDVFIO.

You mean HostIOMMUDeviceVFIO and HostIOMMUDeviceVDPA?

I wonder what are the difference between their implementations.

Main reason for asking this is that we have alloc_hwpt (and will
have alloc_viommu soon) too, and should that/those be a part of
the Class op(s) too?

> @@ -833,6 +834,11 @@ static bool hiod_iommufd_vfio_realize(HostIOMMUDevice *hiod, void *opaque,
>      caps->type = type;
>      caps->hw_caps = hw_caps;
>  
> +    idev = HOST_IOMMU_DEVICE_IOMMUFD(hiod);
> +    idev->iommufd = vdev->iommufd;
> +    idev->devid = vdev->devid;
> +    idev->hwpt_id = vdev->hwpt->hwpt_id;

Since it's the default hwpt that VFIO contain allocated, perhaps
it's better to call it default_hwpt_id, indicating that won't be
changed by further HWPT attachment.

Thanks
Nicolin