On 3/20/2025 20:22, Jason Wang wrote:
On Fri, Mar 21, 2025 at 12:45 AM Konstantin Shkolnyy <k...@linux.ibm.com> wrote:
On 3/19/2025 19:58, Jason Wang wrote:
On Thu, Mar 20, 2025 at 12:34 AM Konstantin Shkolnyy <k...@linux.ibm.com> wrote:
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.
The mlx5 driver doesn't do anything for VHOST_VDPA_SET_CONFIG. Intel's
driver, however, apparently stores the configuration. So, it appears,
Intel will avoid the problem... Perhaps mlx5 could do the same so that
QEMU can set the address before it starts the VM (QEMU doesn't have to
later let the VM change the config).
The problem is that config space is not allowed to be written, that is
why mlx5 doesn't implement the write method.
Conceptually, setting the address
by QEMU cmdline doesn't look different from setting it by "vdpa dev add".
It's kind of different.
E.g the device may not even have VIRTIO_NET_F_MAC feature etc.
I'm not sure I understand... This is the MAC address returned by
VHOST_VDPA_GET_CONFIG. If mlx5 allows it to be set by "vdpa dev add",
shouldn't it also allow it to be set by VHOST_VDPA_SET_CONFIG called by
virtio_net_device_realize(), before the VM exists.
When VM starts running, it queries this MAC address and QEMU fetches it
by VHOST_VDPA_GET_CONFIG. But, because VHOST_VDPA_SET_CONFIG hasn't
stored it, it fetches a wrong stale address.
