Hi Eric On Thu, Feb 27, 2020 at 9:50 PM Auger Eric <eric.au...@redhat.com> wrote: > > Hi Daniel, > > On 2/27/20 12:17 PM, Daniel P. Berrangé wrote: > > On Fri, Feb 14, 2020 at 02:27:35PM +0100, Eric Auger wrote: > >> This series implements the QEMU virtio-iommu device. > >> > >> This matches the v0.12 spec (voted) and the corresponding > >> virtio-iommu driver upstreamed in 5.3. All kernel dependencies > >> are resolved for DT integration. The virtio-iommu can be > >> instantiated in ARM virt using: > >> > >> "-device virtio-iommu-pci". > > > > Is there any more documentation besides this ? > > not yet in qemu. > > > > I'm wondering on the intended usage of this, and its relation > > or pros/cons vs other iommu devices > > Maybe if you want to catch up on the topic, looking at the very first > kernel RFC may be a good starting point. Motivation, pros & cons were > discussed in that thread (hey, April 2017!) > https://lists.linuxfoundation.org/pipermail/iommu/2017-April/021217.html > > on ARM we have SMMUv3 emulation. But the VFIO integration is not > possible because SMMU does not have any "caching mode" and my nested > paging kernel series is blocked. So the only solution to integrate with > VFIO is looming virtio-iommu. > > In general the pros that were put forward are: virtio-iommu is > architecture agnostic, removes the burden to accurately model complex > device states, driver can support virtualization specific optimizations > without being constrained by production driver maintenance. Cons is perf > and mem footprint if we do not consider any optimization. > > You can have a look at > > http://events17.linuxfoundation.org/sites/events/files/slides/viommu_arm.pdf > Thanks for the patches.
Could I ask one question? To support vSVA and pasid in guest, which direction you recommend, virtio-iommu or vSMMU (your nested paging) Do we still have any obstacles? Would you mind give some breakdown. Jean mentioned PASID still not supported in QEMU. Thanks