[PATCH] virtio_pci: support enabling VFs

Rustad, Mark D
Wed, 30 May 2018 16:44:07 -0000

On May 30, 2018, at 9:22 AM, Michael S. Tsirkin <mst at redhat.com> wrote:

>> +static int virtio_pci_sriov_configure(struct pci_dev *pci_dev, int
>> num_vfs)
>> +{
>> +	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
>> +	struct virtio_device *vdev = &vp_dev->vdev;
>> +	int (*sriov_configure)(struct pci_dev *pci_dev, int num_vfs);
>> +
>> +	if (!(vdev->config->get_status(vdev) &
VIRTIO_CONFIG_S_DRIVER_OK))
>> +		return -EBUSY;
>> +
>> +	if (!__virtio_test_bit(vdev, VIRTIO_F_SR_IOV))
>> +		return -EINVAL;
>> +
>> +	sriov_configure = pci_sriov_configure_simple;
>> +	if (sriov_configure == NULL)
>> +		return -ENOENT;
>
> BTW what is all this trickery in aid of?

When SR-IOV support is not compiled into the kernel,
pci_sriov_configure_simple is #defined as NULL. This allows it to compile
in that case, even though there is utterly no way for it to be called in
that case. It is an alternative to #ifs in the code.

--
Mark Rustad, Networking Division, Intel Corporation
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