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

[Peter Maydell]

On 25 June 2018 at 12:07, Sameeh Jubran <address@hidden> wrote:
> From: Sameeh Jubran <address@hidden>
>
> 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".

thanks
-- PMM