RE: [PATCH] raw/ntb: add check for DB intr handler registering

["Guo, Junfeng" <junfeng.guo@intel.com>]

> -----Original Message-----
> From: Guo, Junfeng
> Sent: Thursday, February 10, 2022 15:18
> To: Wu, Jingjing <jingjing.wu@intel.com>
> Cc: dev@dpdk.org; stable@dpdk.org
> Subject: RE: [PATCH] raw/ntb: add check for DB intr handler registering
> 
> 
> 
> > -----Original Message-----
> > From: Wu, Jingjing <jingjing.wu@intel.com>
> > Sent: Thursday, February 10, 2022 15:05
> > To: Guo, Junfeng <junfeng.guo@intel.com>
> > Cc: dev@dpdk.org; stable@dpdk.org
> > Subject: RE: [PATCH] raw/ntb: add check for DB intr handler registering
> >
> >
> >
> > > -----Original Message-----
> > > From: Guo, Junfeng <junfeng.guo@intel.com>
> > > Sent: Thursday, February 10, 2022 2:29 PM
> > > To: Wu, Jingjing <jingjing.wu@intel.com>
> > > Cc: dev@dpdk.org; stable@dpdk.org; Guo, Junfeng
> > <junfeng.guo@intel.com>
> > > Subject: [PATCH] raw/ntb: add check for DB intr handler registering
> > >
> > > The callback registering of doorbell interrupt handler should be
> > > finished before enabling the interrupt event fd. Thus add the return
> > > value check for this callback registering.
> > >
> > > Fixes: 62012a76811e ("raw/ntb: add handshake process")
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Junfeng Guo <junfeng.guo@intel.com>
> > > ---
> > >  drivers/raw/ntb/ntb.c | 8 ++++++--
> > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/raw/ntb/ntb.c b/drivers/raw/ntb/ntb.c
> > > index cc611dfbb9..0801e6d1ae 100644
> > > --- a/drivers/raw/ntb/ntb.c
> > > +++ b/drivers/raw/ntb/ntb.c
> > > @@ -1403,8 +1403,12 @@ ntb_init_hw(struct rte_rawdev *dev,
> struct
> > rte_pci_device
> > > *pci_dev)
> > >
> > >  	intr_handle = pci_dev->intr_handle;
> > >  	/* Register callback func to eal lib */
> > > -	rte_intr_callback_register(intr_handle,
> > > -				   ntb_dev_intr_handler, dev);
> > > +	ret = rte_intr_callback_register(intr_handle,
> > > +					 ntb_dev_intr_handler, dev);
> > > +	if (ret) {
> > > +		NTB_LOG(ERR, "Unable to register doorbell intr
> > handler.");
> > > +		return ret;
> > > +	}
> > When will this register failure happen? Have you checked what is the
> root
> > cause?
> 
> When bind with vfio-pci, the DB interrupt callback function often cannot
> work as expected.
> I think this is due to that, the intr callback registering not finished before
> event fd enabled.
> Add the check of the return value here can make sure about correct
> processing sequence.

I think some compiler optimization would lead to this condition.
So add return value check can prevent this (i.e., registering not finished).

> 
> >
> > >
> > >  	ret = rte_intr_efd_enable(intr_handle, hw->db_cnt);
> > >  	if (ret)
> > Need roll back, such as rte_intr_callback_unregister is required when
> fail
> > or driver remove?
> > > --
> > > 2.25.1