Re: [PATCH] virtio_pci: support enabling VFs

From: Rustad, Mark D
Date: Wed May 30 2018 - 12:44:19 EST


On May 30, 2018, at 9:22 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> 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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