Re: [PATCH v4 7/8] docs/microvm.txt: document the new microvm machine type

[Paolo Bonzini <pbonzini@redhat.com>]

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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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