Re: [Qemu-ppc] [PATCH 0/2] RFC: powerpc-vfio: adding support

[Alex Williamson]

On Thu, 2012-07-12 at 14:16 +1000, Alexey Kardashevskiy wrote:
> On 12/07/12 12:54, Alex Williamson wrote:
> > On Wed, 2012-07-11 at 12:25 +1000, Alexey Kardashevskiy wrote:
> >> On 11/07/12 02:57, Alex Williamson wrote:
> >>> On Tue, 2012-07-10 at 15:51 +1000, Alexey Kardashevskiy wrote:
> >>>> The two patches in this set are supposed to add VFIO support for POWER.
> >>>>
> >>>> The first one adds one more step in the initalizaion sequence which I am 
> >>>> not
> >>>> sure is correct.
> >>>>
> >>>> The second patch adds actual VFIO support. It is not ready to submit but
> >>>> ready to discuss. I would like to get rid of all #ifdef TARGET_PPC64 in 
> >>>> patch #2
> >>>> and I wonder if there is any plan to implement some generic EOI support 
> >>>> code, etc.
> >>>
> >>> A generic EOI notifier is on my todo list, but I have no idea what it's
> >>> going to look like.  As you know, I've got an ioapic specific notifier
> >>> in my tree, you add a spapr specific one.  I welcome ideas on how to
> >>> create something generic that has a chance of being accepted.  Thanks,
> >>
> >>
> >> So far the only platform specific call is xxxx_add_gsi_eoi_notifier. The
> >> xxxx_remove_gsi_eoi_notifier only calls notifier_remove, you've got to fix 
> >> yours
> >> ioapic_remove_gsi_eoi_notifier() as it does too much :)
> >>
> >>
> >> The only place for placing "add_eoi" callback I can see right now is 
> >> QEMUMachine as there is no
> >> unified machine interrupt controller - IOAPIC has its own type 
> >> TYPE_IOAPIC_COMMON and XICS is not
> >> even a SysBusDevice. And the callback is not specific for any kind of bus 
> >> so it cannot go to PCIBus.
> >>
> >> Does it sound reasonable?
> > 
> > I suspect we'd need to somehow tie it into qemu_irq where both handlers
> > and notifiers are allocated so we don't really care the underlying
> > implementation.  Something like qemu_add_irq_eoi_notifier(qemu_irq
> > irq, ...).  It's another mess like adding the PCIBus interrupt line to
> > gsi effort though.  Thanks,
> 
> 
> Tried. Added add_eoi_notifier() callback to qemu_irq, new IRQ allocator:
> qemu_irq *qemu_allocate_irqs2(qemu_irq_handler handler, void *opaque, int n,
>                               qemu_eoi_add_notifier add_notifier);
> and called it from the XICS initialization code.
> 
> It could work out if pci_get_irq() or pci_route_irq_fn() returned qemu_irq 
> but no, they just return
> a global IRQ number (pure or embedded in a struct) and there is no common way 
> to resolve qemu_irq
> (and then add_eoi_notifier()) from that number within vfio_pci.

Well GSI and qemu_irq are different address spaces.  We still need GSI
for any kind of qemu bypass case.

> May be we could add the callback pointer into PCIINTxRoute?

Maybe, but why is this PCI specific?  Can't we call it as
qemu_add_irq_eoi_notifier(pdev->irq[0], Notifier)?  That would work much
like qemu_set_irq, extracting the irq number from the IRQState and
passing it through to the add_notifier callback for IRQState until it
got to the ioapic/pic/xics.

int qemu_add_irq_eoi_notifier(qemu_irq *irq, Notifier notifier)
{
    if (!irq || !irq->add_eoi_notifier)
        return -1;

   return irq->add_eoi_notifier(irq->opaque, irq->n, notifier);
}