On Thursday 21 May 2009, Avi Kivity wrote: > Paul Brook wrote: > >> kvm implements the APIC in the host kernel (qemu upstream doesn't > >> support this yet). The fast path is wired to the in-kernel APIC, not > >> the cpu core directly. > >> > >> The idea is to wire it to UIO for device assignment, to a virtio-device > >> implemented in the kernel, and to qemu. > > > > I still don't see why you're trying to bypass straight from the pci layer > > to the apic. Why can't you just pass the apic MMIO writes to the kernel? > > You've presumably got to update the apic state anyway. > > The fast path is an eventfd so that we don't have to teach all the > clients about the details of MSI. Userspace programs the MSI details > into kvm and hands the client an eventfd. All the client has to do is > bang on the eventfd for the interrupt to be queued. The eventfd > provides event coalescing and is equally useful from the kernel and > userspace, and can be used with targets other than kvm. So presumably if a device triggers an APIC interrupt using a write that isn't one of the currently configured PCI devices, it all explodes horribly? Paul -- 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
