On Tue, May 21, 2024 at 05:13:50PM -0700, Nicolin Chen wrote: > Yea. VMM is always allowed to create a viommu to wrap an S2 > HWPT. Then, I assume iommufd in this case should allocate a > viommu object if !domain_ops->viommu_alloc. Yeah > On one side, it may not be straightforward for a qemu viommu > driver to hold a shared S2 hwpt, as the driver is typically > per instance, though I think it can keep viommu to its own. > So passing the S2 hwpt back to qemu core and tie to iommufd > handler (ictx) makes sense. Yes, qemu will need some per-driver-type but not per-instance storage to make this work. Ie the ARM per-driver-type shared storage would hold the ARM specific list of S2 hwpts. > On the other side, there can be some future HW potentially > supporting two+ kinds of IO page tables so a VM may have two+ > S2 hwpts? Then the core would hold a list of S2 hwpts and the > viommu driver would need to try-n-allocate viommu against the > list.. Yes, it is supported in the API. Userspace should try to create viommus with all the S2 hwpts available and build a new one if it can't, just like hwpt attachment to a device. Jason
