Re: [PATCH 0/4] virtio_net: vdpa: update MAC address when it is generated by virtio-net

[Laurent Vivier]

On 1/22/23 11:23, Michael S. Tsirkin wrote:
> On Sun, Jan 22, 2023 at 11:05:22AM +0100, Laurent Vivier wrote:
> > When the MAC address is not provided by the vdpa device virtio_net
> > driver assigns a random one without notifying the device.
> > The consequence, in the case of mlx5_vdpa, is the internal routing
> > tables of the device are not updated and this can block the
> > communication between two namespaces.
> >
> > To fix this problem, use virtnet_send_command(VIRTIO_NET_CTRL_MAC)
> > to set the address from virtnet_probe() when the MAC address is
> > randomly assigned from virtio_net.
> >
> > While I was testing this change I found 3 other bugs in vdpa_sim_net:
> >
> > - vdpa_sim_net sets the VIRTIO_NET_F_MAC even if no MAC address is
> >    provided. So virtio_net doesn't generate a random MAC address and
> >    the MAC address appears to be 00:00:00:00:00:00
> >
> > - vdpa_sim_net never processes the command and virtnet_send_command()
> >    hangs in an infinite loop. To avoid a kernel crash add a timeout
> >    in the loop.
> >
> > - To allow vdpa_sim_net to process the command, replace the cpu_relax()
> >    in the loop by a schedule(). vdpa_sim_net uses a workqueue to process
> >    the queue, and if we don't allow the kernel to schedule, the queue
> >    is not processed and the loop is infinite.
>
> I'd split these things out as opposed to a series unless there's
> a dependency I missed.

We needed to fix virtio_net before fixing vdpa_sim_net otherwise the 
virtnet_send_command() hangs when we define the vdpa device with "vdpa dev" but without a 
MAC address.

> All this reminds me of
> https://lore.kernel.org/r/20221226074908.8154-5-jasowang%40redhat.com
>
> how is this patch different/better?
> Pls also CC people involved in that original discussion.

I was not aware of the Jason's series.

It seems to address better the problem, except it triggers the ASSERT_RTNL() in 
virtnet_send_command() when it is called from virtnet_probe().

I will remove patches 2 and 4 from my series.
PATCH 3 can be sent on independently too.

Thanks,
Laurent