On 3/9/2026 12:33 PM, Jason Wang wrote:
On Mon, Mar 9, 2026 at 10:37 AM Yui Washizu <[email protected]> wrote:
Recent QEMU versions added support for virtio SR-IOV emulation,
allowing virtio devices to expose SR-IOV VFs to the guest.
However, virtio_bus does not implement the num_vf callback of bus_type,
causing dev_num_vf() to return 0 for virtio devices even when
SR-IOV VFs are active.
net/core/rtnetlink.c calls dev_num_vf(dev->dev.parent) to populate
IFLA_NUM_VF and IFLA_VFINFO_LIST
Patch looks good but,
If I understand correctly, ndo_get_vf_config is needed for
IFLA_VFINFO_LIST but not implemeted in this patch?
Thank you for your comment.
I submitted this patch because I confirmed
that "ip link show" returns the correct VF IDs with this implementation.
In the current implementation,
I believe there is no information that would need to be referenced
through IFLA_VFINFO_LIST.
Therefore, I did not include ndo_get_vf_config in this patch,
as it did not seem essential at this stage.
Would it be better to implement IFLA_VFINFO_LIST support together with this?
Regards,
in RTM_GETLINK responses. For a
virtio-net device, dev.parent points to the virtio_device, whose bus
is virtio_bus. Without num_vf, SR-IOV VF information is silently
omitted from tools that rely on rtnetlink, such as 'ip link show'.
Add a num_vf callback that delegates to dev_num_vf(dev->parent),
which in turn reaches the underlying transport (pci_bus_type for
virtio-pci) where the actual VF count is tracked. Non-PCI transports
are unaffected as dev_num_vf() returns 0 when no num_vf callback is
present.
Signed-off-by: Yui Washizu <[email protected]>
---
drivers/virtio/virtio.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 5bdc6b82b30b..299fa83be1d5 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -435,6 +435,14 @@ static void virtio_dev_shutdown(struct device *_d)
dev->config->reset(dev);
}
+static int virtio_dev_num_vf(struct device *dev)
+{
+ struct virtio_device *vdev = dev_to_virtio(dev);
+
+ return dev_num_vf(vdev->dev.parent);
+}
+
+
static const struct bus_type virtio_bus = {
.name = "virtio",
.match = virtio_dev_match,
@@ -444,6 +452,7 @@ static const struct bus_type virtio_bus = {
.remove = virtio_dev_remove,
.irq_get_affinity = virtio_irq_get_affinity,
.shutdown = virtio_dev_shutdown,
+ .num_vf = virtio_dev_num_vf,
};
int __register_virtio_driver(struct virtio_driver *driver, struct module
*owner)
--
2.47.3
Thanks
