On 17 September 2016 at 16:28, Ard Biesheuvel [off-list ref] wrote:

Another thing to keep in mind is that GICv2
compatibility is disabled on the non-secure side if the secure side
elects to configure its view of the GIC as v3 (i.e., in order to
support >8 cores)

If I'm reading the 'legacy configurations' chapter of the GICv3
spec correctly, that is true for the NS host OS (ie the one
handling physical interrupts) but a guest OS can still use
the old GICv2-compat interface (assuming it was implemented
in silicon at all).

thanks
-- PMM