Re: [PATCH v7 4/8] vhost: rxtx: use queue id instead of constant ring index

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Wed, Oct 21, 2015 at 01:31:55PM +0300, Michael S. Tsirkin wrote:
> On Wed, Oct 21, 2015 at 11:48:10AM +0800, Yuanhan Liu wrote:
> > From: Changchun Ouyang <changchun.ouyang@intel.com>
> > 
> > Do not use VIRTIO_RXQ or VIRTIO_TXQ anymore; use the queue_id
> > instead, which will be set to a proper value for a specific queue
> > when we have multiple queue support enabled.
> > 
> > For now, queue_id is still set with VIRTIO_RXQ or VIRTIO_TXQ,
> > so it should not break anything.
> > 
> > Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> > Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> > Acked-by: Flavio Leitner <fbl@sysclose.org>
> 
> I tried to figure out how is queue_id set and I couldn't.

queue_id is set outside the DPDK library, it's up to application
to select a queue. There was a demo (examples/vhost/vhost-switch)
before, and it was removed. (check the cover letter for the reason).

> Please note that for virtio devices, guest is supposed to
> control the placement of incoming packets in RX queues.

I may not follow you.

Enqueuing packets to a RX queue is done at vhost lib, outside the
guest, how could the guest take the control here?

	--yliu

> > ---
> > 
> > v7: commit title fix
> > ---
> >  lib/librte_vhost/vhost_rxtx.c | 46 ++++++++++++++++++++++++++++++-------------
> >  1 file changed, 32 insertions(+), 14 deletions(-)
> > 
> > diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
> > index 7026bfa..14e00ef 100644
> > --- a/lib/librte_vhost/vhost_rxtx.c
> > +++ b/lib/librte_vhost/vhost_rxtx.c
> > @@ -42,6 +42,16 @@
> >  
> >  #define MAX_PKT_BURST 32
> >  
> > +static inline int __attribute__((always_inline))
> > +is_valid_virt_queue_idx(uint32_t virtq_idx, int is_tx, uint32_t max_qp_idx)
> > +{
> > +	if ((is_tx ^ (virtq_idx & 0x1)) ||
> > +	    (virtq_idx >= max_qp_idx * VIRTIO_QNUM))
> > +		return 0;
> > +
> > +	return 1;
> > +}
> > +
> >  /**
> >   * This function adds buffers to the virtio devices RX virtqueue. Buffers can
> >   * be received from the physical port or from another virtio device. A packet
> > @@ -68,12 +78,14 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
> >  	uint8_t success = 0;
> >  
> >  	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_rx()\n", dev->device_fh);
> > -	if (unlikely(queue_id != VIRTIO_RXQ)) {
> > -		LOG_DEBUG(VHOST_DATA, "mq isn't supported in this version.\n");
> > +	if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->virt_qp_nb))) {
> > +		RTE_LOG(ERR, VHOST_DATA,
> > +			"%s (%"PRIu64"): virtqueue idx:%d invalid.\n",
> > +			__func__, dev->device_fh, queue_id);
> >  		return 0;
> >  	}
> >  
> > -	vq = dev->virtqueue[VIRTIO_RXQ];
> > +	vq = dev->virtqueue[queue_id];
> >  	count = (count > MAX_PKT_BURST) ? MAX_PKT_BURST : count;
> >  
> >  	/*
> > @@ -235,8 +247,9 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
> >  }
> >  
> >  static inline uint32_t __attribute__((always_inline))
> > -copy_from_mbuf_to_vring(struct virtio_net *dev, uint16_t res_base_idx,
> > -	uint16_t res_end_idx, struct rte_mbuf *pkt)
> > +copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
> > +			uint16_t res_base_idx, uint16_t res_end_idx,
> > +			struct rte_mbuf *pkt)
> >  {
> >  	uint32_t vec_idx = 0;
> >  	uint32_t entry_success = 0;
> > @@ -264,7 +277,7 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint16_t res_base_idx,
> >  	 * Convert from gpa to vva
> >  	 * (guest physical addr -> vhost virtual addr)
> >  	 */
> > -	vq = dev->virtqueue[VIRTIO_RXQ];
> > +	vq = dev->virtqueue[queue_id];
> >  	vb_addr = gpa_to_vva(dev, vq->buf_vec[vec_idx].buf_addr);
> >  	vb_hdr_addr = vb_addr;
> >  
> > @@ -464,11 +477,14 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
> >  
> >  	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_merge_rx()\n",
> >  		dev->device_fh);
> > -	if (unlikely(queue_id != VIRTIO_RXQ)) {
> > -		LOG_DEBUG(VHOST_DATA, "mq isn't supported in this version.\n");
> > +	if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->virt_qp_nb))) {
> > +		RTE_LOG(ERR, VHOST_DATA,
> > +			"%s (%"PRIu64"): virtqueue idx:%d invalid.\n",
> > +			__func__, dev->device_fh, queue_id);
> > +		return 0;
> >  	}
> >  
> > -	vq = dev->virtqueue[VIRTIO_RXQ];
> > +	vq = dev->virtqueue[queue_id];
> >  	count = RTE_MIN((uint32_t)MAX_PKT_BURST, count);
> >  
> >  	if (count == 0)
> > @@ -509,8 +525,8 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
> >  							res_cur_idx);
> >  		} while (success == 0);
> >  
> > -		entry_success = copy_from_mbuf_to_vring(dev, res_base_idx,
> > -			res_cur_idx, pkts[pkt_idx]);
> > +		entry_success = copy_from_mbuf_to_vring(dev, queue_id,
> > +			res_base_idx, res_cur_idx, pkts[pkt_idx]);
> >  
> >  		rte_compiler_barrier();
> >  
> > @@ -562,12 +578,14 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
> >  	uint16_t free_entries, entry_success = 0;
> >  	uint16_t avail_idx;
> >  
> > -	if (unlikely(queue_id != VIRTIO_TXQ)) {
> > -		LOG_DEBUG(VHOST_DATA, "mq isn't supported in this version.\n");
> > +	if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->virt_qp_nb))) {
> > +		RTE_LOG(ERR, VHOST_DATA,
> > +			"%s (%"PRIu64"): virtqueue idx:%d invalid.\n",
> > +			__func__, dev->device_fh, queue_id);
> >  		return 0;
> >  	}
> >  
> > -	vq = dev->virtqueue[VIRTIO_TXQ];
> > +	vq = dev->virtqueue[queue_id];
> >  	avail_idx =  *((volatile uint16_t *)&vq->avail->idx);
> >  
> >  	/* If there are no available buffers then return. */
> > -- 
> > 1.9.0