[Qemu-devel] Guest IOMMU and Cisco usnic

[Benoît Canet]

Hi Alex,

After the IRC conversation we had a few days ago I understood that guest IOMMU
was not implemented.

I have a real use case for it:

Cisco usnic allow to write MPI applications while driving the network card in
userspace in order to optimize the latency. It's made for compute clusters.

The typical cloud provider don't provide bare metal access but only vms on top
of Cisco's hardware hence VFIO is using the IOMMU to passthrough the NIC to the
guest and no IOMMU is present in the guest.

questions: Would writing a performing guest IOMMU implementation be possible ?
           How complex this project looks for someone knowing IOMMUs issues ?

The ideal implementation would forward the IOMMU work to the host hardware for
speed.

I can devote time writing the feature if it's doable.

Best regards

Benoît