Re: [dpdk-dev] [PATCH] igb_uio: remove device reset in open

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 1 Nov 2017 06:58:53 +0000
"Mody, Rasesh" <Rasesh.Mody@cavium.com> wrote:

> Hi Jianfeng and Ferruh,
> 
> > From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
> > Sent: Thursday, October 26, 2017 5:50 PM
> > 
> > On 10/26/2017 2:28 AM, Tan, Jianfeng wrote:  
> > > Hi Rasesh,
> > >
> > >
> > > On 10/26/2017 7:43 AM, Mody, Rasesh wrote:  
> > >> Hi Ferruh,
> > >>  
> > >>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ferruh Yigit
> > >>> Sent: Friday, October 20, 2017 9:58 AM
> > >>>
> > >>> On 10/20/2017 9:55 AM, Ferruh Yigit wrote:  
> > >>>> Remove device reset during application start, the reset for
> > >>>> application exit still there.
> > >>>>
> > >>>> Reset in open removed because of following comments:
> > >>>> 1- Device reset not completed when VF driver loaded, which cause VF  
> > PMD  
> > >>>>     initialization error.
> > >>>>     Adding delay can solve the issue but will increase driver load time.
> > >>>>
> > >>>> 2- Reset will be issues all devices unconditionally, not very efficient
> > >>>>     way.
> > >>>>
> > >>>> Fixes: b58eedfc7dd5 ("igb_uio: issue FLR during open and release of
> > >>>> device file")
> > >>>> Cc: stable@dpdk.org
> > >>>>
> > >>>> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>  
> > >>> Hi Jingjing, Shijith, Gregory, Harish,
> > >>>
> > >>> Can you please test this on top of current master (which has already
> > >>> Jingjin's
> > >>> fix) ?  
> > >> The original FLR change during igb_uio open()/release() in DPDK17.08 also  
> > impacts BNX2X PMD and it exhibits the issues with bare metal testing.  
> > >>
> > >> Now, we tested this change for BNX2X PMD using latest dpdk, which has  
> > this fix where FLR is invoked only in the release().
> > 
> > Good to hear this fixed the problem.  
> 
> Yes, it fixed the issue caused by pci reset during application start.
> 
> >   
> > >> However, we ran into an issue when trying to reload the testpmd  
> > application in quick succession. The pci reset, called during the igb_uio
> > release() operation, is taking longer time and adapter is still doing the FLR
> > when we relaunch the application. We see this behavior with bare metal
> > testing.  
> > >
> > > If we don't reset that device, it will continue working which is a
> > > more serious issue IMO.  
> > 
> > +1  
> 
> I think, it would better for the individual PMDs to take care of the reset during the application exit.

That will never be possible. Poll Mode Drivers are userspace entities and part of the application. If application crashes, there is no way for PMD to do cleanup, it must
be handled by kernel.