On 25/09/19 17:04, Sergio Lopez wrote: > I'm going back to this level of the thread, because after your > suggestion I took a deeper look at how things work around the PIC, and > discovered I was completely wrong about my assumptions. > > For virtio-mmio devices, given that we don't have the ability to > configure vectors (as it's done in the PCI case) we're stuck with the > ones provided by the platform PIC, which in the x86 case is the i8259 > (at least from Linux's perspective). > > So we can get rid of the IOAPIC, but we need to keep the i8259 (we have > both a userspace and a kernel implementation too, so it should be fine). Hmm... I would have thought the vectors are just GSIs, which will be configured to the IOAPIC if it is present. Maybe something is causing Linux to ignore the IOAPIC? > As for the PIT, we can omit it if we're running with KVM acceleration, > as kvmclock will be used to calculate loops per jiffie and avoid the > calibration, leaving it enabled otherwise. Can you make it an OnOffAuto property, and default to on iff !KVM? Paolo
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