On Mon, Nov 30, 2015 at 10:34:07AM +0200, Michael S. Tsirkin wrote: > We know vring num is a power of 2, so use & > to mask the high bits. > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > --- > drivers/vhost/vhost.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 080422f..85f0f0a 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1366,10 +1366,12 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, > /* Only get avail ring entries after they have been exposed by guest. */ > smp_rmb(); > > + } > + Oops. This sneaked in from an unrelated patch. Pls ignore, will repost. > /* Grab the next descriptor number they're advertising, and increment > * the index we've seen. */ > if (unlikely(__get_user(ring_head, > - &vq->avail->ring[last_avail_idx % vq->num]))) { > + &vq->avail->ring[last_avail_idx & (vq->num - 1)]))) { > vq_err(vq, "Failed to read head: idx %d address %p\n", > last_avail_idx, > &vq->avail->ring[last_avail_idx % vq->num]); > @@ -1489,7 +1491,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq, > u16 old, new; > int start; > > - start = vq->last_used_idx % vq->num; > + start = vq->last_used_idx & (vq->num - 1); > used = vq->used->ring + start; > if (count == 1) { > if (__put_user(heads[0].id, &used->id)) { > @@ -1531,7 +1533,7 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads, > { > int start, n, r; > > - start = vq->last_used_idx % vq->num; > + start = vq->last_used_idx & (vq->num - 1); > n = vq->num - start; > if (n < count) { > r = __vhost_add_used_n(vq, heads, n); > -- > MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html