before

/*
 * num_vfs > 0; number of vfs to enable
 * num_vfs = 0; disable all vfs
 *
 * Note: SRIOV spec doesn't allow partial VF
 *       disable, so its all or none.
 */
static ssize_t sriov_numvfs_store(struct device *dev,
                                  struct device_attribute *attr,
                                  const char *buf, size_t count)
{
        struct pci_dev *pdev = to_pci_dev(dev);
        int num_vfs_enabled = 0;
        int num_vfs;
        int ret = 0;
        u16 total;

        if (kstrtoint(buf, 0, &num_vfs) < 0)
                return -EINVAL;

        /* is PF driver loaded w/callback */
        if (!pdev->driver || !pdev->driver->sriov_configure) {
                dev_info(&pdev->dev,
                         "Driver doesn't support SRIOV configuration via sysfs\n");
                return -ENOSYS;
        }

        /* if enabling vf's ... */
        total = pci_sriov_get_totalvfs(pdev);
        /* Requested VFs to enable < totalvfs and none enabled already */
        if ((num_vfs > 0) && (num_vfs <= total)) {
                if (pdev->sriov->num_VFs == 0) {
                        num_vfs_enabled =
                                pdev->driver->sriov_configure(pdev, num_vfs);
                        if ((num_vfs_enabled >= 0) &&
                            (num_vfs_enabled != num_vfs)) {
                                dev_warn(&pdev->dev,
                                         "Only %d VFs enabled\n",
                                         num_vfs_enabled);
                                return count;
                        } else if (num_vfs_enabled < 0)
                                /* error code from driver callback */
                                return num_vfs_enabled;
                } else if (num_vfs == pdev->sriov->num_VFs) {
                        dev_warn(&pdev->dev,
                                 "%d VFs already enabled; no enable action taken\n",
                                 num_vfs);
                        return count;
                } else {
                        dev_warn(&pdev->dev,
                                 "%d VFs already enabled. Disable before enabling %d VFs\n",
                                 pdev->sriov->num_VFs, num_vfs);
                        return -EINVAL;
                }
        }

        /* disable vfs */
        if (num_vfs == 0) {
                if (pdev->sriov->num_VFs != 0) {
                        ret = pdev->driver->sriov_configure(pdev, 0);
                        return ret ? ret : count;
                } else {
                        dev_warn(&pdev->dev,
                                 "All VFs disabled; no disable action taken\n");
                        return count;
                }
        }

        dev_err(&pdev->dev,
                "Invalid value for number of VFs to enable: %d\n", num_vfs);

        return -EINVAL;
}