[dpdk-dev] [PATCH] eal: fix max number of interrupt request

[Zhang, Qi Z]

Hi Thomas:

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> Sent: Friday, February 10, 2017 6:19 PM
> To: Zhang, Qi Z <qi.z.zhang at intel.com>
> Cc: dev at dpdk.org; Wu, Jingjing <jingjing.wu at intel.com>
> Subject: Re: [PATCH] eal: fix max number of interrupt request
> 
> 2017-02-09 14:59, Qi Zhang:
> > The max number of interrupt request is possible be changed after
> > rte_intr_callback_register, so in get_max_intr, we need to check if
> > nessesary to update the max_intr.
> 
> So you are using rte_intr_enable() to update the max_intr field in the case of
> VFIO_MSIX.
> What about MSI, INTX and UIO cases?

My thought is, even without my fix, VFIO_MSIX is already the only case that try to modify max_intr field 
In get_max_intr, we have:
				if (!src->intr_handle.max_intr)
                        src->intr_handle.max_intr = 1;
                else if (src->intr_handle.max_intr > RTE_MAX_RXTX_INTR_VEC_ID)
                        src->intr_handle.max_intr
                                = RTE_MAX_RXTX_INTR_VEC_ID + 1;
So my patch just follow this and fix some problem.

Another option is I can use a local variable that assigned by max_intr with boundary check, so get_max_intr can be totally removed and max_intr in intr_source will not be modified.

To me both fix are not perfect, I think the problem is in rte_intr_callback_register we just save a copy of the pci_dev->intr_handle but not the address point, so we are missing some mechanism to sync them.
But since we have tight schedule on the 17.02 release and this issue does cause some example code can't work, so we need to a fix it first, we may consider improve the mechanism later.

Thanks
Qi