Re: [Qemu-devel] Question about the vfio device interrupt

[Li Qiang]

Auger Eric <address@hidden> 于2019年5月15日周三 下午6:16写道：

> Hi,
>
> On 5/15/19 12:01 PM, Li Qiang wrote:
> > Hello Paolo, Alex and all,
> >
> > In vfio_intx_enable_kvm(qemu) I see we associate a resamplefd with the
> > umask function(vfio_pci_intx_unmask_handler in linux).
> >
> >     irq_set = g_malloc0(argsz);
> >     irq_set->argsz = argsz;
> >     irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD |
> VFIO_IRQ_SET_ACTION_UNMASK;
> >     irq_set->index = VFIO_PCI_INTX_IRQ_INDEX;
> >     irq_set->start = 0;
> >     irq_set->count = 1;
> >     pfd = (int32_t *)&irq_set->data;
> >
> >     *pfd = irqfd.resamplefd;
> >
> >     ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_SET_IRQS, irq_set);
> >
> > I know this resamplefd is triggered when the interrupt controller
> receives
> > an EOI and
> > then we unmask and re-enabled the VFIO devices' interrupt.
> >
> > So I think there  there must be a mask process(so we unmask it later), I
> > mean there must a
> > call of function vfio_pci_set_intx_mask(in linux).
> >
> > What I can't understand is when this process(mask VFIO devices'
> interrupt)
> > occurs?
> It is done in the VFIO interrupt handler:
> vfio_intx_handler/disable_irq_nosync for VFIO PCI (vfio_pci_intrs.c) or
> vfio_automasked_irq_handler (vfio_platform_irq.c) for VFIO PLATFORM .
>
>
Thanks Eric,

Got it.
I just forget to look at the interrupt handler(vfio_intx_handler)!


Thanks,
Li Qiang



> Thanks
>
> Eric
>
> > I only find a place(vfio_basic_config_write) calls vfio_pci_intx_mask> I
> think when the guest process the interrupt it may mask this
> > interrupt(finally call vfio_pci_set_intx_mask), but I can't find the code
> > path related with vfio_basic_config_write.
> >
> >
> > Any hints?
> >
> > Thanks,
> > Li Qiang
> >
>