IOMMU paravirtualization and Xen IOMMU subsystem rework

As a follow-up to https://xcp-ng.org/blog/2024/04/18/iommu-paravirtualization-for-xen/, I would like to improve the paravirtualized IOMMU interface design, and discuss more on the implementation side.

Due to current IOMMU subsystem of Xen limitations for this feature, I tried a redesign on the IOMMU subsystem but it lacks feedback from the community, and implementation has several challenges.

I would like to discuss on the :

• PV-IOMMU design proposal : https://lists.xenproject.org/archives/html/xen-devel/2024-04/msg01304.html
• Xen IOMMU subsystem changes proposal : https://lists.xenproject.org/archives/html/xen-devel/2024-04/msg01303.html
• interactions with existing features (quarantine, …)
• future uses of this (SPDK/DPDK in Dom0, VT-d emulation with QEMU, …)