Re: [PATCH 0/3] reference implementation of RSS

[Michael S. Tsirkin]

On Fri, Mar 06, 2020 at 11:50:30AM +0200, Yuri Benditovich wrote:
> 
> 
> On Fri, Mar 6, 2020 at 11:27 AM Jason Wang <address@hidden> wrote:
> 
> 
>     On 2020/2/27 上午1:48, Yuri Benditovich wrote:
>     > Support for VIRTIO_NET_F_RSS feature in QEMU for reference
>     > purpose. Implements Toeplitz hash calculation for incoming
>     > packets according to configuration provided by driver.
>     >
>     > This series requires previously submitted and accepted
>     > patch to be applied:
>     > https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg06448.html
>     >
>     > Yuri Benditovich (3):
>     >    virtio-net: introduce RSS RX steering feature
>     >    virtio-net: implement RSS configuration command
>     >    virtio-net: implement RX RSS processing
>     >
>     >   hw/net/trace-events                         |   3 +
>     >   hw/net/virtio-net.c                         | 234
>     +++++++++++++++++++-VIRTIO_NET_F_RSS
>     >   include/hw/virtio/virtio-net.h              |  12 +
>     >   include/standard-headers/linux/virtio_net.h |  37 +++-
>     >   4 files changed, 273 insertions(+), 13 deletions(-)
>     >
> 
>     One question before the reviewing.
> 
>     Do we need to deal with migration (which I think yes)?
> 
> 
> I think we don't (yet) as this is a reference implementation and the main goal
> is to provide the functional reference for hardware solution.


That's fine, but then we must block migration, and add appropriate code
comments. Just silently losing data isn't a good idea.

> I agree with the general direction that for complete support of RSS and hash
> delivery the best way is to do that in kernel using bpf.
> For that, IMO, the bpf should be a part of the kernel (it uses skb fields) and
> the tap should receive just RSS parameters for it.
> At this stage we definitely will need to add migration support and propagation
> of RSS parameters.
>  
> 
> 
>     Thanks
> 
>