On 2011-12-04 14:31, Avi Kivity wrote: > On 12/03/2011 01:17 PM, Jan Kiszka wrote: >> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >> >> Introduce the alternative 'kvm-i8259' device model that exploits KVM >> in-kernel acceleration. >> >> The PIIX3 initialization code is furthermore extended by KVM specific >> IRQ route setup. Moreover, GSI injection differs in KVM mode from the >> user space model. As we can dispatch ISA-range IRQs to both IOAPIC and >> PIC inside the kernel, we do not need to inject them separately. This is >> reflected by a KVM-specific GSI handler. >> >> + >> +qemu_irq *kvm_i8259_init(void) >> +{ >> + ISADevice *dev; >> + >> + dev = isa_create("kvm-i8259"); >> > > Same issue. Is this a different device, or an different implementation > of the same device? They are theoretically the same from guest perspective (therefore you can migrate between machines that differ in this). > > We're forcing migration from 1.0 to 1.1 to disable in-kernel irqchip on > the target. For qemu itself, that's no issue. But for qemu-kvm, it > will result in loss of performance, or hacks to alias the two back together. We should this happen with qemu-kvm? The vmstates are compatible, thus you can migration from old qemu-kvm in-kernel devices to the new kvm-* ones (once they are feature-equivalent). Not sure how much hacks this may require to qemu-kvm, but I don't think it should make the situation worse for that tree. Jan
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