On Mon, Nov 30, 2020 at 04:00:51AM -0500, Michael S. Tsirkin wrote:
> On Mon, Nov 30, 2020 at 08:27:46AM +0200, Eli Cohen wrote:
> > On Sun, Nov 29, 2020 at 03:08:22PM -0500, Michael S. Tsirkin wrote:
> > > On Sun, Nov 29, 2020 at 08:43:51AM +0200, Eli Cohen wrote:
> > > > We should not try to use the VF MAC address as that is used by the
> > > > regular (e.g. mlx5_core) NIC implementation. Instead, use a random
> > > > generated MAC address.
> > > >
> > > > Suggested by: Cindy Lu <l...@redhat.com>
> > > > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5
> > > > devices")
> > > > Signed-off-by: Eli Cohen <e...@nvidia.com>
> > >
> > > I didn't realise it's possible to use VF in two ways
> > > with and without vdpa.
> >
> > Using a VF you can create quite a few resources, e.g. send queues
> > recieve queues, virtio_net queues etc. So you can possibly create
> > several instances of vdpa net devices and nic net devices.
> >
> > > Could you include a bit more description on the failure
> > > mode?
> >
> > Well, using the MAC address of the nic vport is wrong since that is the
> > MAC of the regular NIC implementation of mlx5_core.
>
> Right but ATM it doesn't coexist with vdpa so what's the problem?
>
This call is wrong: mlx5_query_nic_vport_mac_address()
> > > Is switching to a random mac for such an unusual
> > > configuration really justified?
> >
> > Since I can't use the NIC's MAC address, I have two options:
> > 1. To get the MAC address as was chosen by the user administering the
> > NIC. This should invoke the set_config callback. Unfortunately this
> > is not implemented yet.
> >
> > 2. Use a random MAC address. This is OK since if (1) is implemented it
> > can always override this random configuration.
> >
> > > It looks like changing a MAC could break some guests,
> > > can it not?
> > >
> >
> > No, it will not. The current version of mlx5 VDPA does not allow regular
> > NIC driver and VDPA to co-exist. I have patches ready that enable that
> > from steering point of view. I will post them here once other patches on
> > which they depend will be merged.
> >
> > https://patchwork.ozlabs.org/project/netdev/patch/20201120230339.651609-12-sae...@nvidia.com/
>
> Could you be more explicit on the following points:
> - which configuration is broken ATM (as in, two device have identical
> macs? any other issues)?
The only wrong thing is the call to mlx5_query_nic_vport_mac_address().
It's not breaking anything yet is wrong. The random MAC address setting
is required for the steering patches.
> - why won't device MAC change from guest point of view?
>
It's lack of implementation in qemu as far as I know.
>
> > > > ---
> > > > drivers/vdpa/mlx5/net/mlx5_vnet.c | 5 +----
> > > > 1 file changed, 1 insertion(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > > b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > > index 1fa6fcac8299..80d06d958b8b 100644
> > > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > > @@ -1955,10 +1955,7 @@ void *mlx5_vdpa_add_dev(struct mlx5_core_dev
> > > > *mdev)
> > > > if (err)
> > > > goto err_mtu;
> > > >
> > > > - err = mlx5_query_nic_vport_mac_address(mdev, 0, 0, config->mac);
> > > > - if (err)
> > > > - goto err_mtu;
> > > > -
> > > > + eth_random_addr(config->mac);
> > > > mvdev->vdev.dma_dev = mdev->device;
> > > > err = mlx5_vdpa_alloc_resources(&ndev->mvdev);
> > > > if (err)
> > > > --
> > > > 2.26.2
> > >
>
