Re: [PATCH 0/16 v6] PCI: Linux kernel SR-IOV support

[Andi Kleen <andi@firstfloor.org>]

Anthony Liguori <anthony@codemonkey.ws> writes:
>
> What we would rather do in KVM, is have the VFs appear in the host as
> standard network devices.  We would then like to back our existing PV
> driver to this VF directly bypassing the host networking stack.  A key
> feature here is being able to fill the VF's receive queue with guest
> memory instead of host kernel memory so that you can get zero-copy
> receive traffic.  This will perform just as well as doing passthrough
> (at least) and avoid all that ugliness of dealing with SR-IOV in the
> guest.

But you shift a lot of ugliness into the host network stack again.
Not sure that is a good trade off.

Also it would always require context switches and I believe one
of the reasons for the PV/VF model is very low latency IO and having
heavyweight switches to the host and back would be against that.

-Andi

-- 
ak@linux.intel.com