On Wed, Aug 10, 2022 at 04:22:41PM +0000, Parav Pandit wrote:
>
> > From: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > Sent: Wednesday, August 10, 2022 12:05 PM
> >
> > On Wed, Aug 10, 2022 at 04:00:08PM +0000, Parav Pandit wrote:
> > >
> > > > From: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > > > Sent: Wednesday, August 10, 2022 5:03 AM
> > > > > >
> > > > > > Should we make this depend on the vq reset ability maybe?
> > > > >
> > > > > The advantage of this is to keep TX working. Or we can use device
> > > > > reset as a fallback if there's no vq reset.
> > > > >
> > > > > Thanks
> > > >
> > > > Device reset is really annoying in that it loses all the state:
> > > > rx filters etc etc.
> > >
> > > The elegant solution is let driver tell the new mtu to the device.
> > > One way to do so is by using existing ctrl vq.
> >
> > That will need a new feature bit.
> >
> Yes. ctrl vq can tell what all configuration does it allow. :)
> Or you prefer feature bit?
We did feature bits for this in the past.
> > > If merged buffer is done, and new mtu is > minimum posting size, no need
> > to undergo vq reset.
> > > If merged buffer is not done, and buffer posted are smaller than new mtu,
> > undergo vq reset optionally.
> >
> > This can be done with or without sending mtu to device.
> Yes, telling mtu to device helps device to optimize and adhere to the spec line " The device MUST NOT pass received packets that exceed mtu" in section 5.1.4.1.
Again, that line refers to \field{mtu} which is the max mtu supported,
irrespective to anything driver does.
--
MST
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