RE: [PATCH v2] net/netvsc: fix number Tx queues > Rx queues

[Alan Elder <alan.elder@microsoft.com>]

Thanks for the feedback Long.

I've made both changes you suggested, plus one additional one to not try and allocate an mbuf if the pool is null.

This means if a packet is received on a Rx queue that isn't being polled we will see it appear as "mbuf allocation failed" rather than causing a segfault.

Cheers,
Alan

> -----Original Message-----
> From: Long Li <longli@microsoft.com>
> Sent: Tuesday, March 12, 2024 7:09 PM
> To: Alan Elder <alan.elder@microsoft.com>; Ferruh Yigit
> <ferruh.yigit@amd.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>
> Cc: dev@dpdk.org; stephen <stephen@networkplumber.org>
> Subject: RE: [PATCH v2] net/netvsc: fix number Tx queues > Rx queues
> 
> > a/drivers/net/netvsc/hn_rxtx.c b/drivers/net/netvsc/hn_rxtx.c index
> > 9bf1ec5509..c0aaeaa972 100644
> > --- a/drivers/net/netvsc/hn_rxtx.c
> > +++ b/drivers/net/netvsc/hn_rxtx.c
> > @@ -243,6 +243,7 @@ hn_dev_tx_queue_setup(struct rte_eth_dev *dev,  {
> >  	struct hn_data *hv = dev->data->dev_private;
> >  	struct hn_tx_queue *txq;
> > +	struct hn_rx_queue *rxq;
> >  	char name[RTE_MEMPOOL_NAMESIZE];
> >  	uint32_t tx_free_thresh;
> >  	int err = -ENOMEM;
> > @@ -301,6 +302,22 @@ hn_dev_tx_queue_setup(struct rte_eth_dev *dev,
> >  		goto error;
> >  	}
> >
> > +	/*
> > +	 * If there are more Tx queues than Rx queues, allocate rx_queues
> > +	 * with event buffer so that Tx completion messages can still be
> > +	 * received
> > +	 */
> > +	if (queue_idx >= dev->data->nb_rx_queues) {
> > +		rxq = hn_rx_queue_alloc(hv, queue_idx, socket_id);
> 
> Need to check if rxq is NULL.
> 
> > +		/*
> > +		 * Don't allocate mbuf pool or rx ring.  RSS is always configured
> > +		 * to ensure packets aren't received by this Rx queue.
> > +		 */
> > +		rxq->mb_pool = NULL;
> > +		rxq->rx_ring = NULL;
> > +		dev->data->rx_queues[queue_idx] = rxq;
> > +	}
> > +
> >  	txq->agg_szmax  = RTE_MIN(hv->chim_szmax, hv->rndis_agg_size);
> >  	txq->agg_pktmax = hv->rndis_agg_pkts;
> >  	txq->agg_align  = hv->rndis_agg_align; @@ -354,6 +371,17 @@ static
> > void hn_txd_put(struct hn_tx_queue *txq, struct hn_txdesc *txd)
> >  	rte_mempool_put(txq->txdesc_pool, txd);  }
> >
> > +static void
> > +hn_rx_queue_free_common(struct hn_rx_queue *rxq) {
> > +	if (!rxq)
> > +		return;
> > +
> > +	rte_free(rxq->rxbuf_info);
> > +	rte_free(rxq->event_buf);
> > +	rte_free(rxq);
> > +}
> > +
> >  void
> >  hn_dev_tx_queue_release(struct rte_eth_dev *dev, uint16_t qid)  { @@
> > -364,6
> > +392,13 @@ hn_dev_tx_queue_release(struct rte_eth_dev *dev, uint16_t
> > +qid)
> >  	if (!txq)
> >  		return;
> >
> > +	/*
> > +	 * Free any Rx queues allocated for a Tx queue without a
> corresponding
> > +	 * Rx queue
> > +	 */
> > +	if (qid >= dev->data->nb_rx_queues)
> > +		hn_rx_queue_free_common(dev->data->rx_queues[qid]);
> > +
> >  	rte_mempool_free(txq->txdesc_pool);
> >
> >  	rte_memzone_free(txq->tx_rndis_mz);
> > @@ -942,6 +977,13 @@ hn_dev_rx_queue_setup(struct rte_eth_dev *dev,
> >  	if (queue_idx == 0) {
> >  		rxq = hv->primary;
> >  	} else {
> > +		/*
> > +		 * If the number of Tx queues was previously greater than
> > +		 * the number of Rx queues, we may already have allocated
> > +		 * an rxq. If so, free it now before allocating a new one.
> > +		 */
> > +		hn_rx_queue_free_common(dev->data-
> > >rx_queues[queue_idx]);
> 
> This logic seems strange. How about check if rxq is already allocated. If not,
> allocate it.
> 
> Something like:
> 
> if (!dev->data->rx_queues[queue_idx])
> 	rxq = hn_rx_queue_alloc(hv, queue_idx, socket_id);
> 
> 
> 
> Thanks,
> 
> Long