On 16/09/2016 14:44, Alexander Graf wrote:

quoted

On 16 Sep 2016, at 14:40, Paolo Bonzini [off-list ref]
wrote:



On 16/09/2016 14:29, Christoffer Dall wrote:

quoted

quoted

It may be useful for migrating a gicv2 VM to a gicv3 host
without gicv2 emulation as well.

I don't see why you'd do this; the VGIC hardware can perfectly
well be used for nesting as well, and this works rather well.

Can GICv3 emulate GICv2 in a guest?

It depends on the gicv3 configuration. As an SOC vendor you can
either enable gicv2 compatibility or disable it. ThunderX for example
is gicv3 only.

And QEMU complains on startup and exits, I hope.

I am not too optimistic about having migration from kernel GIC to
userspace GIC, honestly.  But GICv2 emulation on GICv3-only hosts is a
very reasonable thing to want, if only for testing/debugging purposes.

Paolo