Re: VDPA Debug/Statistics

[Roopa Prabhu]

On 8/11/20 5:44 AM, Michael S. Tsirkin wrote:
> External email: Use caution opening links or attachments
>
>
> On Tue, Aug 11, 2020 at 11:58:23AM +0000, Eli Cohen wrote:
> > On Tue, Aug 11, 2020 at 11:26:20AM +0000, Eli Cohen wrote:
> > > Hi All
> > >
> > > Currently, the only statistics we get for a VDPA instance comes from the virtio_net device instance. Since VDPA involves hardware acceleration, there can be quite a lot of information that can be fetched from the underlying device. Currently there is no generic method to fetch this information.
> > >
> > > One way of doing this can be to create a the host, a net device for
> > > each VDPA instance, and use it to get this information or do some
> > > configuration. Ethtool can be used in such a case
> > >
> > > I would like to hear what you think about this or maybe you have some other ideas to address this topic.
> > >
> > > Thanks,
> > > Eli
> > Something I'm not sure I understand is how are vdpa instances created on mellanox cards? There's a devlink command for that, is that right?
> > Can that be extended for stats?
> >
> > Currently any VF will be probed as VDPA device. We're adding devlink support but I am not sure if devlink is suitable for displaying statistics. We will discuss internally but I wanted to know why you guys think.
> OK still things like specifying the mac are managed through rtnetlink,
> right?
>
> Right now it does not look like you can mix stats and vf, they are
> handled separately:
>
>          if (rtnl_fill_stats(skb, dev))
>                  goto nla_put_failure;
>
>          if (rtnl_fill_vf(skb, dev, ext_filter_mask))
>                  goto nla_put_failure;
>
> but ability to query vf stats on the host sounds useful generally.
>
> As another option, we could use a vdpa specific way to retrieve stats,
> and teach qemu to report them.

If you are looking for a place to add additional stats, please, check 
the RTM_*STATS api

https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/net/core/rtnetlink.c#n5351
(Its a place where new interface and protocol stats are being added)