On 3/20/2025 01:54, Eugenio Perez Martin wrote:
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?
The problem happens when the cmdline address (new) is different from the
current one in the VDPA device (old), whether the old one has been set
by "vdpa dev add" or by an earlier VM run.
In other words, it's generally not possible to run a VM with an
arbitrary address - it'll have to inherit whatever the VDPA device
already has. (Except for the very first run and _only_ if "vdpa dev add"
didn't specify the address (leaving it "6 zero bytes"), or specified the
same one as the cmdline.)
Therefore, it's not possible to omit the address in the libvirt XML and
let libvirt generate it.
