On Thu, Mar 20, 2025 at 1:59 AM Jason Wang <jasow...@redhat.com> wrote: > > Adding Cindy and Eugenio > > On Thu, Mar 20, 2025 at 12:34 AM Konstantin Shkolnyy <k...@linux.ibm.com> > wrote: > > > > I’m observing a problem while testing VDPA with Nvidia ConnectX-6 (mlx5) > > on s390. > > > > Upon start, virtio_net_device_realize() tries to set a new MAC address > > by VHOST_VDPA_SET_CONFIG which doesn’t do anything. > > > > Later, the VM gets started and learns about the old address from > > virtio_net_get_config() which returns whatever VHOST_VDPA_GET_CONFIG > > returns, unless it's "6 zero bytes", in which case it instead returns > > the desired new address (and the problem is avoided). > > > > Then QEMU again tries to set the new address from vhost_net_start(), now > > by calling vhost_vdpa_net_load_cmd(...,VIRTIO_NET_CTRL_MAC, > > VIRTIO_NET_CTRL_MAC_ADDR_SET, ...). This time the new address is > > successfully programmed into the NIC, but the VM doesn't know about it. > > Have you enabled shadow virtqueue? If yes, does it work if you don't do that? >
Either you're using SVQ or not, is cmdline nic mac address the same as the provided with the vdpa command? > > > > As the result, the VM now sends packets with a source address on which > > the NIC doesn’t listen. > > > > Upon reading this forum, I see that VHOST_VDPA_SET_CONFIG is > > “deprecated”, and so VIRTIO_NET_CTRL_MAC_ADDR_SET must be the right > > method, but it’s apparently called too late. > > VHOST_VDPA_SET_CONFIG requires the vDPA parent support which is not > necessarily there. > VIRTIO_NET_CTRL_MAC_ADDR_SET requires the shadow virtqueue as well as > the CTRL_MAC_ADDR support. > Nit, VIRTIO_NET_CTRL_MAC_ADDR_SET does not require SVQ. You are not able to migrate if SVQ cannot be enabled, for example, because it does not support a given feature. > Neither of them seems robust. > > > Or maybe > > virtio_net_get_config() needs to always return the desired new address > > and not the old one from VHOST_VDPA_GET_CONFIG? > > > > I’m looking for an opinion/direction from someone who knows this code. > > > > As it is, the only VDPA scenario that's working for me is: > > 1) Avoid specifying the MAC address in the "vdpa dev add" command (which > > will create the "6 zero bytes" condition on the first launch). > > 2) Keep using the same MAC address for every subsequent VM launch on the > > same NIC "virtual function" (so that the old and new addresses are the > > same). > > This is the way we currently use it. Is there any limitation of this? > > Thanks > > > >
