long vfio_pci_ioeventfd()

in pci/vfio_pci_rdwr.c [413:500]
70 lines of code
17 McCabe index (conditional complexity)

long vfio_pci_ioeventfd(struct vfio_pci_core_device *vdev, loff_t offset,
			uint64_t data, int count, int fd)
{
	struct pci_dev *pdev = vdev->pdev;
	loff_t pos = offset & VFIO_PCI_OFFSET_MASK;
	int ret, bar = VFIO_PCI_OFFSET_TO_INDEX(offset);
	struct vfio_pci_ioeventfd *ioeventfd;

	/* Only support ioeventfds into BARs */
	if (bar > VFIO_PCI_BAR5_REGION_INDEX)
		return -EINVAL;

	if (pos + count > pci_resource_len(pdev, bar))
		return -EINVAL;

	/* Disallow ioeventfds working around MSI-X table writes */
	if (bar == vdev->msix_bar &&
	    !(pos + count <= vdev->msix_offset ||
	      pos >= vdev->msix_offset + vdev->msix_size))
		return -EINVAL;

#ifndef iowrite64
	if (count == 8)
		return -EINVAL;
#endif

	ret = vfio_pci_setup_barmap(vdev, bar);
	if (ret)
		return ret;

	mutex_lock(&vdev->ioeventfds_lock);

	list_for_each_entry(ioeventfd, &vdev->ioeventfds_list, next) {
		if (ioeventfd->pos == pos && ioeventfd->bar == bar &&
		    ioeventfd->data == data && ioeventfd->count == count) {
			if (fd == -1) {
				vfio_virqfd_disable(&ioeventfd->virqfd);
				list_del(&ioeventfd->next);
				vdev->ioeventfds_nr--;
				kfree(ioeventfd);
				ret = 0;
			} else
				ret = -EEXIST;

			goto out_unlock;
		}
	}

	if (fd < 0) {
		ret = -ENODEV;
		goto out_unlock;
	}

	if (vdev->ioeventfds_nr >= VFIO_PCI_IOEVENTFD_MAX) {
		ret = -ENOSPC;
		goto out_unlock;
	}

	ioeventfd = kzalloc(sizeof(*ioeventfd), GFP_KERNEL);
	if (!ioeventfd) {
		ret = -ENOMEM;
		goto out_unlock;
	}

	ioeventfd->vdev = vdev;
	ioeventfd->addr = vdev->barmap[bar] + pos;
	ioeventfd->data = data;
	ioeventfd->pos = pos;
	ioeventfd->bar = bar;
	ioeventfd->count = count;
	ioeventfd->test_mem = vdev->pdev->resource[bar].flags & IORESOURCE_MEM;

	ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler,
				 vfio_pci_ioeventfd_thread, NULL,
				 &ioeventfd->virqfd, fd);
	if (ret) {
		kfree(ioeventfd);
		goto out_unlock;
	}

	list_add(&ioeventfd->next, &vdev->ioeventfds_list);
	vdev->ioeventfds_nr++;

out_unlock:
	mutex_unlock(&vdev->ioeventfds_lock);

	return ret;
}