On 2011-10-17 12:56, Avi Kivity wrote: > On 10/17/2011 11:27 AM, Jan Kiszka wrote: >> So far we deliver MSI messages by writing them into the target MMIO >> area. This reflects what happens on hardware, but imposes some >> limitations on the emulation when introducing KVM in-kernel irqchip >> models. For those we will need to track the message origin. > > Why do we need to track the message origin? Emulated interrupt remapping?
The origin holds the routing cache which we need to track if the message already has a route (and that without searching long lists) and to update that route instead of add another one. > >> Moreover, >> different architecture or accelerators may want to overload the delivery >> handler. >> >> Therefore, this commit introduces a delivery hook that is called by the >> MSI/MSI-X layer when devices send normal messages, but also on spurious >> deliveries that ended up on the APIC MMIO handler. Our default delivery >> handler for APIC-based PCs then dispatches between real MSIs and other >> DMA requests that happened to take the MSI patch. > > 'path' > >> >> -static void apic_send_msi(target_phys_addr_t addr, uint32_t data) >> +void apic_deliver_msi(MSIMessage *msg) > > In general, it is better these days to pass small structures by value. OK, will adjust this. > > > Not sure what the gain is from intercepting the msi just before the > stl_phys() vs. in the apic handler. APIC is x86-specific, MSI is not. I think Xen will also want to make use of this hook. I originally though of using it for the KVM in-kernel models as well, but I will now establish a callback at APIC-level (upstream will look differently from qemu-kvm in this regard). Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
