On Thu, Jan 05, 2017 at 11:09:14AM +0800, Jason Wang wrote: > > > On 2017年01月05日 02:57, John Fastabend wrote: > > [...] > > > > > On 2017年01月04日 00:48, John Fastabend wrote: > > > > On 17-01-02 10:14 PM, Jason Wang wrote: > > > > > On 2017年01月03日 06:30, John Fastabend wrote: > > > > > > XDP programs can not consume multiple pages so we cap the MTU to > > > > > > avoid this case. Virtio-net however only checks the MTU at XDP > > > > > > program load and does not block MTU changes after the program > > > > > > has loaded. > > > > > > > > > > > > This patch sets/clears the max_mtu value at XDP load/unload time. > > > > > > > > > > > > Signed-off-by: John Fastabend <john.r.fastab...@intel.com> > > > > > > --- > > [...] > > > > > > OK so this logic is a bit too simply. When it resets the max_mtu I > > > > guess it > > > > needs to read the mtu via > > > > > > > > virtio_cread16(vdev, ...) > > > > > > > > or we may break the negotiated mtu. > > > Yes, this is a problem (even use ETH_MAX_MTU). We may need a method to > > > notify > > > the device about the mtu in this case which is not supported by virtio > > > now. > > Note this is not really a XDP specific problem. The guest can change the MTU > > after init time even without XDP which I assume should ideally result in a > > notification if the MTU is negotiated. > > Yes, Michael, do you think we need add some mechanism to notify host about > MTU change in this case? > > Thanks
Why does host care?
