On 13/07/2015 12:25, Andre Przywara wrote: > > For using MSIs in a guest when running on an ARM(64) system using a > GICv3 interrupt controller we need to have a device ID available. On > real hardware this information is sampled from the bus by the ITS part > of the interrupt controller. > To make this work for guests, we need to extend two ioctls which deal > with MSIs: KVM_SIGNAL_MSI and KVM_SET_GSI_ROUTING. > > The idea that we sketched so far in [1] and [2] is to use a new > capability (KVM_CAP_MSI_DEVID) to advertise both a flag bit for > KVM_SIGNAL_MSI and a new type for KVM_SET_GSI_ROUTING. > > Since current kernels bail out on any flag value != 0 in KVM_SIGNAL_MSI, > we need the new capability to tell userland about it in a reliable and > portable way (to avoid hacks like #ifdef ARM && USES_IRQ_ROUTING in > userland). > > For KVM_SET_GSI_ROUTING there was the idea of using the very same flag > value in it's own flag field, but I find it saner to use a new routing > type instead (KVM_IRQ_ROUTING_EXTENDED_MSI). Both approaches would > piggy-back on the existing struct kvm_irq_routing_msi and re-purpose the > pad field in there. I think I prefer the flag. Offhand it sounds easier to add support for it to non-ARM architectures, compared to KVM_IRQ_ROUTING_EXTENDED_MSI. > Summarized: > 1) Add a new KVM_CAP_MSI_DEVID to advertise the device ID extension. > 2) Use a KVM_MSI_VALID_DEVID flag in KVM_SIGNAL_MSI to re-purpose part > of struct kvm_msi. These two sounds good. Paolo > 3) Add a new routing type KVM_IRQ_ROUTING_EXTENDED_MSI for > KVM_SET_GSI_ROUTING to add device IDs in struct kvm_irq_routing_msi. > > Is that a sensible way to extend the KVM API? -- 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
