On Wed, Jul 30, 2025 at 10:51:13AM +0000, Duan, Zhenzhong wrote:
> >> 2. there can also be more than one vIOMMUs with different user
> >> configuration, e.g., arm smmuv3.
That's correct. But would you please elaborate how different user
configurations would benefit from this new op? I don't see a good
reasoning behind that.
> >> 4. It's too late for VFIO to call get_viommu_cap() after set_iommu_device()
> >> because we need get_viommu_cap() to determine if creating nested
> >parent
> >> hwpt or not at attaching stage, meanwhile hiod realize needs
> >iommufd,
> >
> >hiod -> "host IOMMU device"
>
> Will do.
>
> >
> >> devid and hwpt_id which are ready after attach_device().
> >
> >I find the above sentence difficult to understand.
>
> This is trying to explain the reason of order between attach_device(),
> get_viommu_cap() and hiod realizing.
> What about:
>
> 4. host IOMMU capabilities are passed to vIOMMU through set_iommu_device()
> interface which have to be after attach_device(), when get_viommu_cap()
> is called in attach_device(), there is no way for vIOMMU to get host
> IOMMU capabilities yet, so only emulated capabilities can be returned.
> See below sequence:
>
> attach_device()
> get_viommu_cap()
> create hwpt
> ...
> vfio_device_hiod_create_and_realize()
> set_iommu_device(hiod)
I think it should be:
vfio_device_attach():
iommufd_cdev_attach():
pci_device_get_viommu_cap() for HW nesting cap
create a nesting parent hwpt
attach device to the hwpt
vfio_device_hiod_create_and_realize() creating hiod
...
pci_device_set_iommu_device(hiod)
?
Thanks
Nicolin
