On Thu, May 21, 2009 at 03:38:56PM +0300, Avi Kivity wrote: > Paul Brook wrote: >>> Instead of writing directly, let's abstract it behind a qemu_set_irq(). >>> This is easier for device authors. The default implementation of the >>> irq callback could write to apic memory, while for kvm we can directly >>> trigger the interrupt via the kvm APIs. >>> >> >> I'm still not convinced. >> >> A tight coupling between PCI devices and the APIC is just going to >> cause us problems later one. I'm going to come back to the fact that >> these are memory writes so once we get IOMMU support they will >> presumably be subject to remapping by that, just like any other memory >> access. >> > > I'm not suggesting the qemu_irq will extend all the way to the apic. > Think of it as connecting the device core with its interrupt unit. > >> Even ignoring that, qemu_irq isn't really the right interface. A MSI is a one- >> off event, not a level state. OTOH stl_phys is exactly the right interface. >> > > The qemu_irq callback should do an stl_phys(). The device is happy > since it's using the same API it uses for non-MSI. The APIC is happy > since it isn't connected directly to the device. stl_phys() is happy > since it sees more traffic and can serve more ads. kvm is happy since > it can hijack the callback to throw the interrupt directly into the > kernel. I like the monetization angle here. >> The KVM interface should be contained within the APIC implementation. >> > > Tricky, but doable. I'd rather keep it simple. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
