Re: [dpdk-dev] [PATCH] ethdev: fix rte_eth_dev_owner_unset

[Matan Azrad <matan@mellanox.com>]

Hi Stephen

From: Stephen Hemminger
> On Tue, 14 Aug 2018 05:52:20 +0000
> Matan Azrad <matan@mellanox.com> wrote:
> 
> > Hi Stephen
> >
> > From: Stephen Hemminger
> > > The rte_eth_dev_owner_unset function is unusable because it always
> > > returns -EINVAL. This is because the magic (unowned) value is
> > > flagged as not valid.
> > >
> >
> > It's OK to raise an error when you do unset for unowned device.
> > It means that unset owner should be called for owned device.
> >
> 
> Original code was broken. The following would always fail.
> 
> 	rte_eth_dev_owner_new(&owner.id);
> 	sprintf(owner.name, "example");
> 	rte_eth_dev_owner_set(port_id, &owner);
> 	rte_eth_dev_owner_unset(port_id, owner.id);
> 
> That is because of:
> 	rte_eth_dev_owner_unset(port_id, owner_id)
> 		_rte_eth_dev_owner_set(port_id, owner_id, &new_owner)
> << new_owner.id == RTE_ETH_DEV_NO_OWNER (0)
> 
> 
> 	if (!rte_eth_is_valid_owner_id(new_owner->id) &&  <<
> new_owner->id == RTE_ETH_DEV_NO_OWNER (which is flagged as invalid)
> 	    !rte_eth_is_valid_owner_id(old_owner_id))
> 		return -EINVAL;
> 

But both should be invalid the new owner and the old owner(&&) to raise an EINVAL error.

In the aforementioned check above the old owner should be valid.

> The failsafe driver never checks the return value, and therefore doesn't see
> that it never clears ownership.