VTBLK_RINGSZ
struct pci_vtblk_ioreq vbsc_ios[VTBLK_RINGSZ];
for (i = 0; i < VTBLK_RINGSZ; i++) {
sc->vbsc_vq.vq_qsize = VTBLK_RINGSZ;
sc->vbsc_cfg.vbc_seg_max = MIN(VTBLK_RINGSZ - 2, BLOCKIF_IOV_MAX);
_Static_assert(VTBLK_RINGSZ <= BLOCKIF_RING_MAX, "Each ring entry must be able to queue a request");