Re: [PATCH v2] ixgbe: Fix disable interrupt twice

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Michael


> 
> On 2016/2/2 19:03, Ananyev, Konstantin wrote:
> >
> 
> [...]
> 
> >>>> I don't think i40e miss it, because it not the right please to disable interrupt.
> >>>> because all interrupts are enabled in init stage.
> >>>>
> >>>> Actually, ixgbe enable the interrupt in init stage, but in dev_start, it disable it
> >>>> first and re-enable, so it just the same with doing nothing about interrupt.
> >>>>
> >>>> Just think below:
> >>>>
> >>>> 1. start the port.(interrupt already enabled in init stage, disable -->
> >>>> re-enable)
> >>>> 2. stop the port.(disable interrupt)
> >>>> 3. start port again(Try to disable, but failed, already disabled)
> >>>>
> >>>> Would you think the code has issue?
> >>> [Zhang, Helin] in ixgbe PMD, it can be seen that uninit() calls dev_close(),
> >>> which calls dev_stop(). So I think the disabling can be done only in dev_stop().
> >>> All others can make use of dev_stop to disable the interrupt.
> >> As I said, if it is in dev_stop, it will has issue when dev_start -->
> >> dev_stop --> dev_start, this also could applied in i40e and fm10k. If
> >> you want to put it in dev_stop, better to remove enable interrupts in
> >> init stage, and only put it in dev_start.
> > We can't remove enabling interrupt at init stage and put it only in dev_start().
> > That means PF couldn't handle interrupts from VF till dev_start() will be executed on PF
> >  - which could never happen.
> > For same reason we can't disable all interrupts in dev_stop().
> > See: http://dpdk.org/ml/archives/dev/2015-November/027238.html
> 
> Hi, Konstantin
> 
> Yes, you are right.
> 
> So the only way to fix this issue should remove it in dev_stop(), and
> left it in uinit() stage, which my patch does.
> 
> Am I right?

Yes, I think so.
PF should be able to receive MBOX interrupts  after dev_stop().
Konstantin

> 
> Thanks,
> Michael
> > Konstantin
> >
> >> Thanks,
> >> Michael
> >>> Regards,
> >>> Helin
> >>>
> >>>> Thanks,
> >>>> Michael
> >>>>
> >>>>> Maybe we can follow fm10k's style.
> >>>>>
> >>>>>> On other hand, if we remove it in dev_stop, any side effect? In ixgbe
> >>>>>> start, it will always disable it first and then re-enable it, so it's safe.
> >>>>> I think you mean we can disable intr anyway even if it has been disabled.
> >>>> Actually, we couldn't, DPDK call VFIO ioctl to kernel to disable interrupts, and
> >>>> if we try disable twice, it will return and error.
> >>>> That's why I mean we need a flag to show the interrupts stats. If it already
> >>>> disabled, we do not need call in to kernel. just return and give a warning
> >>>> message.
> >>>>
> >>>> Thanks,
> >>>> Michael
> >>>>
> >>>>>  Sounds more like why we don't
> >>>>> need this patch :)
> >>>>>
> >>>>>> Thanks,
> >>>>>> Michael
> >