[Qemu-devel] virtio + virtq + iommu

[Anshul Makkar]

Hi,

Was tracing the buffer handling code flow after the kick has been
initiated from the guest in case of virtio.

Found this function
cpu_physical_memory_map->address_space_map->address_space_translate
which calls address_space_translate_internal and iommu->translate (get
the translation from TLB) to get the corresponding host virtual
address where I think the packet buffer is mapped to (from guest
physical to host virtual).

So, should I conclude that there is no hardware IOMMU involved in this
translation. QEMU maintains its own TLB and translation mapping which
is used. Or iommu->translate leads to hardware MMU call.

We are developing a high speed packet transfer mechanism using
infiniband cards. So, trying to analyse every possible bottleneck.

Confused here, please suggest.

Anshul Makkar
www.justkernel.com