Re: [virtio-comment] [PATCH v10] virtio-net: Clarify VLAN filter table configuration

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jan 26, 2023 at 04:42:29PM +0000, Parav Pandit wrote:
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Thursday, January 26, 2023 11:31 AM
> > 
> > On Thu, Jan 26, 2023 at 04:27:47PM +0000, Parav Pandit wrote:
> > >
> > >
> > > > From: Michael S. Tsirkin <mst@redhat.com>
> > > > Sent: Thursday, January 26, 2023 12:08 AM
> > > >
> > > > On Wed, Jan 25, 2023 at 11:46:58PM +0000, Parav Pandit wrote:
> > > > > > > but vlans are different aren't they? Anyway changing that will
> > > > > > > need a new feature bit.
> > > > > > I do not the history for about "Note" on why it was made best effort.
> > > > > > To best of my knowledge, it should not be best effort.
> > > > > > Device should not overflow the table. It should fail the ADD call.
> > > >
> > > > For the MAC table?  Failing commands generally is a bad way to
> > > > communicate to drivers.
> > > Failing the command when device cannot do the job is right way to tell the
> > driver to follow the contract in general terms.
> > 
> > There's no contract though. My point is that table size is not in the spec. As long
> > as that is the case failing because it's too big is a bad idea.
> > 
> I agree that table size should be in the spec.
> But I am not convinced that a device should return a fake success and do something wonky behavior.
> For some legacy reason it may have been done, but spec guideline should not be to return some fake success..
> 
> > > > So for VLANs this was added by Tiwei. I guess it looked sane then
> > > > but now I don't remember the motivation. Tiwei CC'd.
> > > > --
> > > > MST
> I get undeliverable reply for Tiwei's email.
> I don't see vlan table being done on best effort in QEMU, nor in mlx5 vdpa device.

No but MAC table is. And with bridge, we rely on management to read vlan
table and update the bridge vlan config. Which happens asynchronously
so again - best effort.


> Si-Wei,
> Do you know any implementation that attempts to do vlan on best effort?
> Otherwise we should clean this up.

Probably too late without a feature bit.

-- 
MST


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