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virtio: add num_vf callback to virtio_bus

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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 in RTM_GETLINK responses.  For a virtio-net device,
dev.parent points to the virtio_device, whose busis 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 <yui.washidu@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260310061454.683894-1-yui.washidu@gmail.com>
This commit is contained in:
Yui Washizu
2026-03-10 15:14:52 +09:00
committed by Michael S. Tsirkin
parent 7222e8c856
commit 82da84282c
1 changed files with 9 additions and 0 deletions
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9
drivers/virtio/virtio.c
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@@ -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)