Re: [PATCH] virtio: fix the vq size issue

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Stephen,

This patch is partially reverting yours:
	http://dpdk.org/browse/dpdk/commit/?id=d78deadae4dca240

A comment or a ack?

2015-07-07 02:32, Ouyang, Changchun:
> 
> > -----Original Message-----
> > From: Ouyang, Changchun
> > Sent: Wednesday, July 1, 2015 3:49 PM
> > To: dev@dpdk.org
> > Cc: Cao, Waterman; Xu, Qian Q; Ouyang, Changchun
> > Subject: [PATCH] virtio: fix the vq size issue
> > 
> > This commit breaks virtio basic packets rx functionality:
> >   d78deadae4dca240e85054bf2d604a801676becc
> > 
> > The QEMU use 256 as default vring size, also use this default value to
> > calculate the virtio avail ring base address and used ring base address, and
> > vhost in the backend use the ring base address to do packet IO.
> > 
> > Virtio spec also says the queue size in PCI configuration is read-only, so virtio
> > front end can't change it. just need use the read-only value to allocate space
> > for vring and calculate the avail and used ring base address. Otherwise, the
> > avail and used ring base address will be different between host and guest,
> > accordingly, packet IO can't work normally.
> > 
> > Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> > ---
> >  drivers/net/virtio/virtio_ethdev.c | 14 +++-----------
> >  1 file changed, 3 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/net/virtio/virtio_ethdev.c
> > b/drivers/net/virtio/virtio_ethdev.c
> > index fe5f9a1..d84de13 100644
> > --- a/drivers/net/virtio/virtio_ethdev.c
> > +++ b/drivers/net/virtio/virtio_ethdev.c
> > @@ -263,8 +263,6 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev,
> >  	 */
> >  	vq_size = VIRTIO_READ_REG_2(hw, VIRTIO_PCI_QUEUE_NUM);
> >  	PMD_INIT_LOG(DEBUG, "vq_size: %d nb_desc:%d", vq_size,
> > nb_desc);
> > -	if (nb_desc == 0)
> > -		nb_desc = vq_size;
> >  	if (vq_size == 0) {
> >  		PMD_INIT_LOG(ERR, "%s: virtqueue does not exist",
> > __func__);
> >  		return -EINVAL;
> > @@ -275,15 +273,9 @@ int virtio_dev_queue_setup(struct rte_eth_dev
> > *dev,
> >  		return -EINVAL;
> >  	}
> > 
> > -	if (nb_desc < vq_size) {
> > -		if (!rte_is_power_of_2(nb_desc)) {
> > -			PMD_INIT_LOG(ERR,
> > -				     "nb_desc(%u) size is not powerof 2",
> > -				     nb_desc);
> > -			return -EINVAL;
> > -		}
> > -		vq_size = nb_desc;
> > -	}
> > +	if (nb_desc != vq_size)
> > +		PMD_INIT_LOG(ERR, "Warning: nb_desc(%d) is not equal to
> > vq size (%d), fall to vq size",
> > +			nb_desc, vq_size);
> > 
> >  	if (queue_type == VTNET_RQ) {
> >  		snprintf(vq_name, sizeof(vq_name), "port%d_rvq%d",
> > --
> > 1.8.4.2
> 
> Any more comments for this patch?
> 
> Thanks
> Changchun
>