sfc: explain that "attached" VFs only refer to Xen

During SRIOV disabling it is checked wether any VF is currently attached
to a guest, using pci_vfs_assigned function. However, this check only
works with VFs attached with Xen, not with vfio/KVM. Added comments
clarifying this point.

Also, replaced manual check of PCI_DEV_FLAGS_ASSIGNED flag and used the
helper function pci_is_dev_assigned instead.
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef10.c

@@ -1070,7 +1070,8 @@ static int efx_ef10_probe_vf(struct efx_nic *efx)
 
 	/* If the parent PF has no VF data structure, it doesn't know about this
 	 * VF so fail probe.  The VF needs to be re-created.  This can happen
-	 * if the PF driver is unloaded while the VF is assigned to a guest.
+	 * if the PF driver was unloaded while any VF was assigned to a guest
+	 * (using Xen, only).
 	 */
 	pci_dev_pf = efx->pci_dev->physfn;
 	if (pci_dev_pf) {

drivers/net/ethernet/sfc/ef10_sriov.c

@@ -122,8 +122,7 @@ static void efx_ef10_sriov_free_vf_vports(struct efx_nic *efx)
 		struct ef10_vf *vf = nic_data->vf + i;
 
 		/* If VF is assigned, do not free the vport  */
-		if (vf->pci_dev &&
-		    vf->pci_dev->dev_flags & PCI_DEV_FLAGS_ASSIGNED)
+		if (vf->pci_dev && pci_is_dev_assigned(vf->pci_dev))
 			continue;
 
 		if (vf->vport_assigned) {
@@ -449,7 +448,9 @@ void efx_ef10_sriov_fini(struct efx_nic *efx)
 	int rc;
 
 	if (!nic_data->vf) {
-		/* Remove any un-assigned orphaned VFs */
+		/* Remove any un-assigned orphaned VFs. This can happen if the PF driver
+		 * was unloaded while any VF was assigned to a guest (using Xen, only).
+		 */
 		if (pci_num_vf(efx->pci_dev) && !pci_vfs_assigned(efx->pci_dev))
 			pci_disable_sriov(efx->pci_dev);
 		return;