Re: [dpdk-dev] [RFC PATCH v3 2/3] eal: add mask and unmask interrupt APIs

["Hyong Youb Kim (hyonkim)" <hyonkim@cisco.com>]

> -----Original Message-----
> From: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
> Sent: Wednesday, July 17, 2019 7:44 PM
> To: Hyong Youb Kim (hyonkim) <hyonkim@cisco.com>; Nithin Kumar
> Dabilpuram <ndabilpuram@marvell.com>; David Marchand
> <david.marchand@redhat.com>; Thomas Monjalon
> <thomas@monjalon.net>; Ferruh Yigit <ferruh.yigit@intel.com>; Bruce
> Richardson <bruce.richardson@intel.com>
> Cc: John Daley (johndale) <johndale@cisco.com>; Shahed Shaikh
> <shshaikh@marvell.com>; dev@dpdk.org
> Subject: RE: [RFC PATCH v3 2/3] eal: add mask and unmask interrupt APIs
> 
> > > I think, it vary from the perspective of IRQ Chip(or controller) vs
> > > NIC
> > > register(Source) PoV.
> > > Since the API starts from rte_intr_* it is more of controller so _ack_
> > > make sense Other reason for ack:
> > > 1) It will enforce that it needs to be called form ISR
> > > 2) It would be have been really correct to unmask if VFIO+MSIx+Linux
> > > supports it
> > > 3) if it is ack, no need to add unmask counterpart, the _mask_ API
> > >
> >
> > Just curious, what you mean by irq controller? Ack/mask/unmask PIOs all
> go
> 
> Programmable Interrupt Controller. Like Intel 8259A, GIC from ARM etc
> The drivers in linux/drivers/irqchip/
> 
> > to the NIC. It is the NIC that asserts/de-asserts irq..
> >
> > > >
> > > > Besides the name, are we agreeing that we want these?
> > > > - Unmask if INTx
> > >
> > > Yes
> > >
> > > > - Nothing if MSI/MSI-X
> > > Yes for MSI over VFIO
> > > No for MSI over UIO/igb_uio
> > >
> >
> > I guess I was not clear. For MSI/MSI-X, we do not want to do mask/unmask
> > regardless of vfio-pci/igb_uio.  Below is my comment about
> > linux/windows/freebsd from an earlier email. Do you disagree? I am sure
> > there are plenty of kernel NIC driver guys here. Please correct me if I am
> > mistaken...
> 
> 
> For some reason, igb_uio kernel driver mask the interrupt for MSIx.
> We need to ack or unmask if needs to work with MSIX + IGB_UIO.
> 
> See
> pci_uio_alloc_resource()
>         if (dev->kdrv == RTE_KDRV_IGB_UIO)
>                 dev->intr_handle.type = RTE_INTR_HANDLE_UIO;
>         else {
>                 dev->intr_handle.type = RTE_INTR_HANDLE_UIO_INTX;
> 
> igbuio_pci_irqcontrol() for masking in kernel.
> 

igb_uio does not auto-mask MSI/MSI-X.

static irqreturn_t
igbuio_pci_irqhandler(int irq, void *dev_id)
{
        struct rte_uio_pci_dev *udev = (struct rte_uio_pci_dev *)dev_id;
        struct uio_info *info = &udev->info;

        /* Legacy mode need to mask in hardware */
        if (udev->mode == RTE_INTR_MODE_LEGACY &&
            !pci_check_and_mask_intx(udev->pdev))
                return IRQ_NONE;

        uio_event_notify(info);

        /* Message signal mode, no share IRQ and automasked */
        return IRQ_HANDLED;
}

Also tested just now with igb_uio. The driver does not need to call
rte_intr_enable(), and it keeps getting interrupts without any issues.

Am I missing something?

-Hyong

> So it is more of making inline with igb_uio kernel driver AND not break
> The existing drivers which was using rte_intr_enable in ISR with
> MSIX+IGB_UIO
> 
> I do agree with that for edge trigged interrupt mask may not require from
> kernel.
> But I am not sure why it is added in igb_uio kernel driver. May  be it is just
> legacy.
> Anyway this wont change schematics, when igb_uio kenrel fixed then the
> counter
> Part can be changed in rte_intr_ack(). Ie. it is transparent to drivers.
> 
> >
> > > I don't  have very strong opinion unmask vs ack. I prefer to have ack
> > > due the reasons stated above.
> > > If you really have strong opinion on using unmask, we will stick with
> > > that to make forward progress.
> > > Let us know.
> > >
> >
> > I have no strong opinion either.
> 
> OK. Lets stick with rte_intr_ack().
> 
> >
> > Thanks..
> > -Hyong