[dpdk-dev] [PATCH 3/3] net/i40e: fix inadvertent override of vector RX allowance

[Zhang, Qi Z]

Hi Muset:

> -----Original Message-----
> From: Ergin, Mesut A
> Sent: Saturday, May 25, 2019 2:09 AM
> To: Zhang, Qi Z <qi.z.zhang at intel.com>; Xing, Beilei <beilei.xing at intel.com>
> Cc: dev at dpdk.org
> Subject: RE: [PATCH 3/3] net/i40e: fix inadvertent override of vector RX
> allowance
> 
> Hi,
> 
> > > > > i40e_rx_vec_dev_conf_condition_check_default(struct rte_eth_dev
> *dev)
> > > > >  	if (rxmode->offloads & DEV_RX_OFFLOAD_VLAN_EXTEND)
> > > > >  		return -1;
> > > > >
> > > > > +	/* Should not override if vector was already disallowed */
> > > >
> > > > It is possible a device be reconfigured between
> > > > dev_stop/dev_start, vector mode may fit for the new configure, so
> > > > the old rx_vec_allowd should be ignored,
> > > >
> > >
> > > i40e_dev_configure would reset rx_vec_allowed already. Am I missing
> > > another reconfiguration path?
> >
> > Look at below scenario,
> >
> > 1. dev_configure (rx_vec_allowed is reset to true) 2. queue_setup (the
> > ring size is not power of 2) 3. dev_start (vector will not be selected
> > due to ring size, rx_vec_allowed set to
> > false)
> > 4. dev_stop
> > 5. queue_setup  (this time, with power of 2 ring size) 6. dev_start
> > (assume vector path should be selected, and rx_vec_allowed should be
> > overwrite to true, but your patch will prevent it)
> >
> > Also, I may not get the point of the gap you observed, would you share
> > more detail scenario?
> >
> > Regards
> > Qi
> 
> It seems like queue setup should reset vector_allowed flag, too. Because
> i40e_dev_rx_queue_setup_runtime is already doing it, though covering only
> half of the state space (i.e. device already started).
> 
> Do you think this patch plus that would be a preferred approach?

First, I need to understand your gap, that might be obvious, but so far I just did not figure out it base your commit log yet, so please give me more heads up :)
Secondary, I think move below codes from dev_configure to dev_start might be a better solution

        ad->rx_bulk_alloc_allowed = true;
        ad->rx_vec_allowed = true;
        ad->tx_simple_allowed = true;
        ad->tx_vec_allowed = true;

Regards
Qi
> 
> >
> > >
> > > Mesut
> > >
> > > > Regards
> > > > Qi
> > > >
> > > > > +	if (!ad->rx_vec_allowed)
> > > > > +	return -1;
> > > > > +
> > > > >  	/**
> > > > >  	 * Vector mode is allowed only when number of Rx queue
> > > > >  	 * descriptor is power of 2.
> > > > > --
> > > > > 2.7.4