Re: [Qemu-devel] [PATCH 05/13] pci: Add pci_device_route_intx_to_irq

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 07, 2012 at 05:10:17PM +0200, Jan Kiszka wrote:
> On 2012-06-07 16:32, Michael S. Tsirkin wrote:
> > On Mon, Jun 04, 2012 at 10:52:13AM +0200, Jan Kiszka wrote:
> >> @@ -1089,6 +1093,14 @@ static void pci_set_irq(void *opaque, int irq_num, int level)
> >>      pci_change_irq_level(pci_dev, irq_num, change);
> >>  }
> >>  
> >> +PCIINTxRoute pci_device_route_intx_to_irq(PCIDevice *dev, int pin)
> >> +{
> >> +    PCIBus *bus = dev->host_bus;
> >> +
> >> +    assert(bus->route_intx_to_irq);
> >> +    return bus->route_intx_to_irq(bus->irq_opaque, dev->host_intx_pin[pin]);
> >> +}
> >> +
> >>  /***********************************************************/
> >>  /* monitor info on PCI */
> >>  
> > 
> > Just an idea: can devices cache this result, bypassing the
> > intx to irq lookup on data path?
> 
> That lookup is part of set_irq which we don't bypass so far and where
> this is generally trivial. If we want to cache the effects of set_irq as
> well, I guess things would become pretty complex (e.g. due to vmstate
> compatibility), and I'm unsure if it would buy us much.

This is less for performance but more for making
everyone use the same infrastructure rather than
assigned devices being the weird case.

> > 
> >> diff --git a/hw/pci.h b/hw/pci.h
> >> index 5b54e2d..bbba01e 100644
> >> --- a/hw/pci.h
> >> +++ b/hw/pci.h
> >> @@ -141,6 +141,15 @@ enum {
> >>  #define PCI_DEVICE_GET_CLASS(obj) \
> >>       OBJECT_GET_CLASS(PCIDeviceClass, (obj), TYPE_PCI_DEVICE)
> >>  
> >> +typedef struct PCIINTxRoute {
> >> +    enum {
> >> +        PCI_INTX_ENABLED,
> >> +        PCI_INTX_INVERTED,
> >> +        PCI_INTX_DISABLED,
> >> +    } mode;
> >> +    int irq;
> >> +} PCIINTxRoute;
> > 
> > Is this INTX route or IRQ route?
> > Is the INTX enabled/disabled/inverted or the IRQ?
> > 
> > I have the impression it's the IRQ, in the apic.
> > PCI INTX are never inverted they are always active low.
> 
> This should be considered as "the route *of* an INTx", not "to some
> IRQ". I could call it PCIINTxToIRQRoute if you prefer, but it's a bit
> lengthy.
> 
> Jan

Yes but the polarity is in apic? Or is it in host bridge?

-- 
MST