On 06/21/2013 04:12 PM, Benjamin Herrenschmidt wrote: > On Fri, 2013-06-21 at 00:03 -0600, Alex Williamson wrote: >> On Fri, 2013-06-21 at 15:12 +1000, Benjamin Herrenschmidt wrote: >>> On Thu, 2013-06-20 at 22:46 -0600, Alex Williamson wrote: >>>> Maybe you could add a device parameter to kvm_irqchip_add_msi_route so >>>> that it can be implemented on POWER without this pci_bus_map_msi >>>> interface that seems very unique to POWER. Thanks, >>> >>> You mean unique to all non-x86 ? :-) >>> >>> I believe almost everybody eventually turn MSIs into "normal" >>> interrupts... >>> >>> Most often than not, the logic to do so is in the PCI Host Bridge. >>> >>> The whole concept of passing the message address/data accross the >>> user/kernel interface is an x86 crackpotery but as is the entire >>> remapping/routing layer so ... :-) >> >> Regardless, this is exactly what kvm_irqchip_add_msi_route does. It >> says, here's an MSIMessage, give me an IRQ that sends that. > > Yes, and in our case, what happens is that the guest said to use "I want > an MSI", we picked up an IRQ, and made up a message for it :-) The > actual message address/data we use is a complete invention that only > exists within qemu. So here we need to basically turn it back into an > IRQ, which we might be able to do by ... just making the message (or > part of the address) be the IRQ number or something like that. > >> In the x86 >> case, that means pick a free IRQ and program it to send that MSIMessage >> when we hit the irqfd. In the case of POWER it means lookup which IRQ >> gets fired by that MSIMessage and return it. In a non-accelerated QEMU >> case I'd think msi_notify() would write the MSIMessage to this IRQ >> remapper device and let it toggle the next qemu_irq down the line. If >> we ever add an IOMMU based IRQ remapper to the x86 model, we'd need >> something similar. Thanks,
Yes, I am changing IRQ to MSI message conversion (and some other things as replacing per PHB MSI windows to one for a whole system) and I am going to post something tonight. -- Alexey
