diff options
Diffstat (limited to 'usr.sbin/bhyve/pci_virtio_net.c')
| -rw-r--r-- | usr.sbin/bhyve/pci_virtio_net.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/usr.sbin/bhyve/pci_virtio_net.c b/usr.sbin/bhyve/pci_virtio_net.c index a5cf8b3..11647d6 100644 --- a/usr.sbin/bhyve/pci_virtio_net.c +++ b/usr.sbin/bhyve/pci_virtio_net.c @@ -172,12 +172,17 @@ hq_num_avail(struct vring_hqueue *hq) { int ndesc; - if (*hq->hq_avail_idx >= hq->hq_cur_aidx) - ndesc = *hq->hq_avail_idx - hq->hq_cur_aidx; - else - ndesc = UINT16_MAX - hq->hq_cur_aidx + *hq->hq_avail_idx + 1; + /* + * We're just computing (a-b) in GF(216). + * + * The only glitch here is that in standard C, + * uint16_t promotes to (signed) int when int has + * more than 16 bits (pretty much always now), so + * we have to force it back to unsigned. + */ + ndesc = (unsigned)*hq->hq_avail_idx - (unsigned)hq->hq_cur_aidx; - assert(ndesc >= 0 && ndesc <= hq->hq_size); + assert(ndesc <= hq->hq_size); return (ndesc); } |
