On Wed, Aug 19, 2015 at 06:51:07PM +0900, Tetsuya Mukawa wrote: > When vhost-user frontend sends GET_VRING_BASE, last used index of vring > should be returned. In DPDK vhost library, 'last_used_idx' represents it. > But the value can be over max index value.
That's true, and I guess it's a design. If you look at the linux kernel vhost code, you will find that there is no such wrap, either. > To return correct value to > vhost frontend, it's needed to be masked. So, it's the frontend job to get the right value, by wrapping it within vring size. --yliu > > Signed-off-by: Tetsuya Mukawa <mukawa at igel.co.jp> > --- > lib/librte_vhost/virtio-net.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c > index b520ec5..144f301 100644 > --- a/lib/librte_vhost/virtio-net.c > +++ b/lib/librte_vhost/virtio-net.c > @@ -661,7 +661,8 @@ get_vring_base(struct vhost_device_ctx ctx, uint32_t > index, > > state->index = index; > /* State->index refers to the queue index. The txq is 1, rxq is 0. */ > - state->num = dev->virtqueue[state->index]->last_used_idx; > + state->num = dev->virtqueue[state->index]->last_used_idx > + & (dev->virtqueue[state->index]->size - 1); > > return 0; > } > -- > 2.1.4