Re: [dpdk-dev] [PATCH v4 2/3] net/iavf: enable PCI bus master after reset

[David Marchand <david.marchand@redhat.com>]

On Wed, May 5, 2021 at 4:56 AM Wang, Haiyue <haiyue.wang@intel.com> wrote:
>
> > -----Original Message-----
> > From: David Marchand <david.marchand@redhat.com>
> > Sent: Tuesday, May 4, 2021 19:32
> > To: Wang, Haiyue <haiyue.wang@intel.com>
> > Cc: dev <dev@dpdk.org>; Zhang, Qi Z <qi.z.zhang@intel.com>; Wang, Liang-min <liang-min.wang@intel.com>;
> > Wu, Jingjing <jingjing.wu@intel.com>; Xing, Beilei <beilei.xing@intel.com>
> > Subject: Re: [PATCH v4 2/3] net/iavf: enable PCI bus master after reset
> >
> > On Tue, Apr 27, 2021 at 4:05 PM Haiyue Wang <haiyue.wang@intel.com> wrote:
> > >
> > > The VF reset can be triggerred by the PF reset event, in this case, the
> > > PCI bus master will be cleared, then the VF is not allowed to issue any
> > > Memory or I/O Requests.
> > >
> > > So after the reset event is detected, always enable the PCI bus master.
> > >
> > > Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
> > > ---
> > >  drivers/net/iavf/iavf_ethdev.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/net/iavf/iavf_ethdev.c b/drivers/net/iavf/iavf_ethdev.c
> > > index d523a0618..9a0a20a29 100644
> > > --- a/drivers/net/iavf/iavf_ethdev.c
> > > +++ b/drivers/net/iavf/iavf_ethdev.c
> > > @@ -2255,6 +2255,9 @@ iavf_dev_close(struct rte_eth_dev *dev)
> > >         rte_free(vf->aq_resp);
> > >         vf->aq_resp = NULL;
> > >
> > > +       if (vf->vf_reset)
> > > +               rte_pci_set_bus_master(pci_dev, true);
> > > +
> > >         vf->vf_reset = false;
> >
> > Not checking for the return code can leave the device in an invalid state.
> > Then after this, calling the init code will fail.
>
> From the upper application's view, if this bus master fix can't recover
> the device into valid state, then the device hotplug API should be used
> to make the device fully recover. So I'd prefer to call bus master "try
> best" to fix. If still have error, the system may be in bad state.

I find it odd to put something required for (re)initialising in a
.dev_close ops.
Maybe the place is more into .dev_reset if you find it confusing in .dev_init.
But this is your driver, I'll let it to your judgement.


On the other hand, what is the point of not failing early/propagating
the rte_pci_set_bus_master error?
The driver can't work without bus master enabled, correct?


-- 
David Marchand