Re: [PATCH 2/2] drivers/net: support single queue per port

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Nov 06, 2024 at 01:19:40PM +0100, Morten Brørup wrote:
> > From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> > Sent: Wednesday, 6 November 2024 12.52
> > 
> > On Fri, Oct 25, 2024 at 11:52:23AM +0000, Morten Brørup wrote:
> > > When configuring DPDK for one queue per port
> > > (#define RTE_MAX_QUEUES_PER_PORT 1), compilation of some network
> > drivers
> > > fails with e.g.:
> > >
> > > ../drivers/net/bnxt/bnxt_rxq.c: In function 'bnxt_rx_queue_stop':
> > > ../drivers/net/bnxt/bnxt_rxq.c:587:34: error: array subscript 1 is
> > above array bounds of 'uint8_t[1]' {aka 'unsigned char[1]'} [-
> > Werror=array-bounds=]
> > >   587 |         dev->data->rx_queue_state[q_id] =
> > RTE_ETH_QUEUE_STATE_STOPPED;
> > >       |         ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
> > > In file included from ../drivers/net/bnxt/bnxt.h:16,
> > >                  from ../drivers/net/bnxt/bnxt_rxq.c:10:
> > > ../lib/ethdev/ethdev_driver.h:168:17: note: while referencing
> > 'rx_queue_state'
> > >   168 |         uint8_t rx_queue_state[RTE_MAX_QUEUES_PER_PORT];
> > >       |                 ^~~~~~~~~~~~~~
> > >
> > > To fix this, a hint is added to the network drivers where a compiler
> > in
> > > the CI has been seen to emit the above error when DPDK is configured
> > for
> > > one queue per port, but we know that the error cannot occur.
> > >
> > > Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> > > ---
> > >  drivers/net/bnxt/bnxt_ethdev.c      |  2 ++
> > >  drivers/net/bnxt/bnxt_rxq.c         |  1 +
> > >  drivers/net/e1000/igb_rxtx.c        |  2 ++
> > >  drivers/net/failsafe/failsafe_ops.c | 10 ++++++++--
> > >  drivers/net/hns3/hns3_rxtx.c        |  2 ++
> > >  drivers/net/mana/tx.c               |  1 +
> > >  6 files changed, 16 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/bnxt/bnxt_ethdev.c
> > b/drivers/net/bnxt/bnxt_ethdev.c
> > > index 1f7c0d77d5..136e308437 100644
> > > --- a/drivers/net/bnxt/bnxt_ethdev.c
> > > +++ b/drivers/net/bnxt/bnxt_ethdev.c
> > > @@ -910,6 +910,7 @@ static int bnxt_start_nic(struct bnxt *bp)
> > >  		struct bnxt_rx_queue *rxq = bp->rx_queues[j];
> > >
> > >  		if (!rxq->rx_deferred_start) {
> > > +			__rte_assume(j < RTE_MAX_QUEUES_PER_PORT);
> > >  			bp->eth_dev->data->rx_queue_state[j] =
> > >  				RTE_ETH_QUEUE_STATE_STARTED;
> > >  			rxq->rx_started = true;
> > > @@ -930,6 +931,7 @@ static int bnxt_start_nic(struct bnxt *bp)
> > >  		struct bnxt_tx_queue *txq = bp->tx_queues[j];
> > >
> > >  		if (!txq->tx_deferred_start) {
> > > +			__rte_assume(j < RTE_MAX_QUEUES_PER_PORT);
> > >  			bp->eth_dev->data->tx_queue_state[j] =
> > >  				RTE_ETH_QUEUE_STATE_STARTED;
> > >  			txq->tx_started = true;
> > > diff --git a/drivers/net/bnxt/bnxt_rxq.c
> > b/drivers/net/bnxt/bnxt_rxq.c
> > > index 1c25c57ca6..1651c26545 100644
> > > --- a/drivers/net/bnxt/bnxt_rxq.c
> > > +++ b/drivers/net/bnxt/bnxt_rxq.c
> > > @@ -584,6 +584,7 @@ int bnxt_rx_queue_stop(struct rte_eth_dev *dev,
> > uint16_t rx_queue_id)
> > >  		return -EINVAL;
> > >  	}
> > >
> > > +	__rte_assume(q_id < RTE_MAX_QUEUES_PER_PORT);
> > >  	dev->data->rx_queue_state[q_id] = RTE_ETH_QUEUE_STATE_STOPPED;
> > >  	rxq->rx_started = false;
> > >  	PMD_DRV_LOG_LINE(DEBUG, "Rx queue stopped");
> > > diff --git a/drivers/net/e1000/igb_rxtx.c
> > b/drivers/net/e1000/igb_rxtx.c
> > > index d61eaad2de..4276bb6d31 100644
> > > --- a/drivers/net/e1000/igb_rxtx.c
> > > +++ b/drivers/net/e1000/igb_rxtx.c
> > > @@ -1868,6 +1868,7 @@ igb_dev_clear_queues(struct rte_eth_dev *dev)
> > >  	struct igb_rx_queue *rxq;
> > >
> > >  	for (i = 0; i < dev->data->nb_tx_queues; i++) {
> > > +		__rte_assume(i < RTE_MAX_QUEUES_PER_PORT);
> > >  		txq = dev->data->tx_queues[i];
> > >  		if (txq != NULL) {
> > >  			igb_tx_queue_release_mbufs(txq);
> > > @@ -1877,6 +1878,7 @@ igb_dev_clear_queues(struct rte_eth_dev *dev)
> > >  	}
> > >
> > >  	for (i = 0; i < dev->data->nb_rx_queues; i++) {
> > > +		__rte_assume(i < RTE_MAX_QUEUES_PER_PORT);
> > >  		rxq = dev->data->rx_queues[i];
> > >  		if (rxq != NULL) {
> > >  			igb_rx_queue_release_mbufs(rxq);
> > 
> > For e1000, this is fine.
> > 
> > Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> > 
> > BTW: is this the only/best way to put in the assumption? If it were me,
> > I'd
> > look to put before the loop the underlying assumption that
> > (dev->data->nb_XX_queues < RTE_MAX_QUEUES_PER_PORT), rather than
> > putting
> > the assumption on "i".
> 
> I would also prefer putting it outside the loop, but it doesn't work in cases where the variable is potentially modified inside the loop. And here's the problem with that: Passing it as a parameter to a logging macro makes the compiler think it is "potentially modified".
> 

That's pretty unfortunate. Thanks for explaining. My ack stands.

/Bruce