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? > > 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. 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 >
