Re: [Qemu-devel] [RFC v2 0/2] Add BPF suuport to Qemu

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Jun 25, 2018 at 02:21:31PM +0300, Sameeh Jubran wrote:
> On Mon, Jun 25, 2018 at 2:16 PM, Peter Maydell <peter.maydell@linaro.org>
> wrote:
> 
> > On 25 June 2018 at 12:07, Sameeh Jubran <sameeh@daynix.com> wrote:
> > > From: Sameeh Jubran <sjubran@redhat.com>
> > >
> > > The Berkeley Packet Filter has been in the kernel for a while now and I
> > > think it is time that it is introduced to Qemu. This patch is an
> > > infrastructure for any future usage of the BPF in Qemu.
> > >
> > > It is important to note that the tun driver had started supporting using
> > > BPF programs through ioctls (TUNSETSTEERINGEBPF and TUNSETFILTEREBPF).
> > > My plan is to use the bpf support from within virtio-net in order to set
> > > a bpf steering program to the tun device which would allow virtio-net to
> > > support RSS feature https://lists.oasis-open.org/
> > archives/virtio-dev/201805/msg00024.html
> > >
> > > Difference from v1:
> > > * Used libbpf library provided by linux
> > > * Added a configure option
> > > * Added a sample patch with demonstrates how to use the libbpf library
> > >   from within virtio-net. This patch should not be applied! It is for
> > >   demonstration purposes only
> > >
> > > The libbpf can be manually installed from the Linux source tree by
> > running make
> > > tools/bpf and make tools/bpf_install from the top level directory.
> >
> > I'm afraid this series still doesn't have a real use case for the
> > library, which is what we would need to be able to review whether
> > using BPF is a sensible design for whatever the underlying
> > feature to be implemented is. That is, what you should be sending
> > is "here is a patchset to implement RSS in virtio-net (and it
> > happens to be implemented using BPF)", not "here is a patchset
> > which links QEMU with libbpf and does nothing else".
> >
> I don't think the infrastructure should be coupled with the implementation.
> These are two separate patch sets, however I can combine them to one.

FWIW, it is perfectly ok to send the code as 2 separate patch sets if you
want to keep them separated. The key point is simply to be able to see a
real implementation.

Regards,
Daniel
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