Re: [dpdk-dev] [PATCH] ethdev: fix switching domain allocation

[Slava Ovsiienko <viacheslavo@mellanox.com>]

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Tuesday, January 14, 2020 17:32
> To: Slava Ovsiienko <viacheslavo@mellanox.com>; dev@dpdk.org
> Cc: Thomas Monjalon <thomas@monjalon.net>; declan.doherty@intel.com;
> stable@dpdk.org
> Subject: Re: [PATCH] ethdev: fix switching domain allocation
> 
> On 12/19/2019 12:47 PM, Viacheslav Ovsiienko wrote:
> > The maximum amount of unique switching domain is supposed to be equal
> > to RTE_MAX_ETHPORTS. The current implementation allows to allocate
> > only RTE_MAX_ETHPORTS-1 domains.
> >
> > Fixes: ce9250406323 ("ethdev: add switch domain allocator")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> > ---
> >  lib/librte_ethdev/rte_ethdev.c | 13 +++++++------
> >  1 file changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/lib/librte_ethdev/rte_ethdev.c
> > b/lib/librte_ethdev/rte_ethdev.c index 6e9cb24..4c2312c 100644
> > --- a/lib/librte_ethdev/rte_ethdev.c
> > +++ b/lib/librte_ethdev/rte_ethdev.c
> > @@ -5065,10 +5065,10 @@ enum rte_eth_switch_domain_state {
> >  	*domain_id = RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID;
> >
> >  	for (i = RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID + 1;
> > -		i < RTE_MAX_ETHPORTS; i++) {
> > -		if (rte_eth_switch_domains[i].state ==
> > +		i <= RTE_MAX_ETHPORTS; i++) {
> > +		if (rte_eth_switch_domains[i - 1].state ==
> >  			RTE_ETH_SWITCH_DOMAIN_UNUSED) {
> > -			rte_eth_switch_domains[i].state =
> > +			rte_eth_switch_domains[i - 1].state =
> >  				RTE_ETH_SWITCH_DOMAIN_ALLOCATED;
> >  			*domain_id = i;
> 
> I would keep the indexes same but change how to set the 'domain_id' to
> "*domain_id = i + 1;", that makes logic simpler.
Agree.

> Would it be simpler if the invalid domain id value used as UINT16_MAX
> instead of '0'? This enables using 'domain_id' as index and prevent this error
> prone indexing.

My concern was not to change the existing RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID
definition, which currently is zero. Currently, AFAIK, the switch feature is supported by mlx5
only, other PMDs do not bother to initialize the rte_eth_dev_info-> switch_info structure
(no one sets RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID to domain_id field for now).
So, changing the RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID from zero might cause
wrong switch capability reporting from PMDs.

> 
> And I think it makes sense to start the loop with "i = 0", instead of
> 'RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID', you are walking through the
> port list, why to involve the 'RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID'
> here.
I do not know why it was implemented in this way 😊
I just was trying to introduce the minimalistic fix. I'll think how to extend my fix a bit.

> 
> >  			return 0;
> > @@ -5082,14 +5082,15 @@ enum rte_eth_switch_domain_state {
> > rte_eth_switch_domain_free(uint16_t domain_id)  {
> >  	if (domain_id == RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID ||
> > -		domain_id >= RTE_MAX_ETHPORTS)
> > +		domain_id > RTE_MAX_ETHPORTS)
> >  		return -EINVAL;
> >
> > -	if (rte_eth_switch_domains[domain_id].state !=
> > +	if (rte_eth_switch_domains[domain_id - 1].state !=
> >  		RTE_ETH_SWITCH_DOMAIN_ALLOCATED)
> >  		return -EINVAL;
> >
> > -	rte_eth_switch_domains[domain_id].state =
> RTE_ETH_SWITCH_DOMAIN_UNUSED;
> > +	rte_eth_switch_domains[domain_id - 1].state =
> > +		RTE_ETH_SWITCH_DOMAIN_UNUSED;
> >
> >  	return 0;
> >  }
> >
With best regards,
Slava