On 23 July 2012 13:26, Avi Kivity <avi@xxxxxxxxxx> wrote: > Really, "irqchip in kernel" means asynchronous interrupts - you can > inject an interrupt from outside the vcpu thread. Obviously if the vcpu > is sleeping you need to wake it up and that pulls in idle management. > > "irqchip" for x86 really means the local APIC, which has a synchronous > interface with the cpu core. "local APIC in kernel" really is > equivalent to "kernel idle management", "KVM_IRQ_LINE", and irqfd. The > ioapic and pit, on the other hand, don't contribute anything to this > (just performance). > So yes, ARM with and without GIC are irqchip_in_kernel, since the > ARM<->GIC interface is asynchronous. Whether to emulate the GIC or not > is just a performance question. So should we be using something other than KVM_CREATE_IRQCHIP to ask the kernel to create a GIC model for us (and leave KVM_CREATE_IRQCHIP as a dummy "always succeed" ioctl)? > So my view is that ARM with and without kernel GIC are > irqchip_in_kernel, since whatever is the local APIC in ARM is always > emulated in the kernel. I'm not sure ARM has any equivalent to the local APIC -- the GIC deals with everything and we don't have any equivalent division of labour to the x86 LAPIC-IOAPIC one. -- PMM -- 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
