On the host side, I'd vote for keeping MSR_KVM_ASYNC_PF_INT for async PF
mechanism only for two reasons:
- We may want to use (currently reserved) upper 56 bits of it for new
asyncPF related features (e.g. flags) and it would be unnatural to add
them to 'MSR_KVM_HYPERVISOR_CALLBACK_INT'
- We should probably leave it to the guest if it wants to share 'suspend
time' notification interrupt with async PF (and if it actually wants to
get one/another).
On the guest side, it is perfectly fine to reuse
HYPERVISOR_CALLBACK_VECTOR for everything.