Re: [PATCH] igb_uio: remove device reset in open

["Mody, Rasesh" <Rasesh.Mody@cavium.com>]

> From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
> Sent: Thursday, November 02, 2017 1:55 AM
> 
> On 11/2/2017 1:03 AM, Mody, Rasesh wrote:
> >> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> >> Sent: Wednesday, November 01, 2017 7:12 AM
> >>
> >> 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.
> >
> > The pci reset in release is breaking the BNX2X PMD. Could we revert this
> reset and get it included with a solution that works for all in the next release?
> 
> Hi Rasesh,
> 
> I am not sure if there is more to do for solution for next releases, and related
> to your case, indeed I wasn't expecting a device reset will take more than
> five minutes...
> 
> Would you be OK to control the reset via a compile time config option, which
> is enabled by default. So you will need to disable it to prevent the reset?

Hi Ferruh,

As I understand, we will have a compile time config option, enabled by default, to guard the pci_reset_function() in the igbuio_pci_release(). We will disable this config option to prevent the reset when using BNX2X.
The controlled reset should work for us.

Thanks!
-Rasesh