graphic: 0.887
performance: 0.827
kernel: 0.799
arm: 0.755
hypervisor: 0.746
device: 0.735
architecture: 0.727
ppc: 0.628
peripherals: 0.626
KVM: 0.622
network: 0.619
semantic: 0.605
PID: 0.546
mistranslation: 0.538
debug: 0.536
register: 0.502
socket: 0.466
vnc: 0.461
risc-v: 0.433
permissions: 0.398
user-level: 0.368
VMM: 0.356
virtual: 0.353
files: 0.316
boot: 0.293
TCG: 0.286
assembly: 0.215
i386: 0.123
x86: 0.099

`-M none` breaks on ARM64 platforms with max IPA size < 40
Description of problem:
QEMU fails to initialize the KVM type properly when `-M none` is used. On ARM64, the KVM type sets the IPA size. Without that setting, the kernel defaults to 40 bits. This fails on machines which cannot support that IPA size, such as Apple M1 machines.

This presumably happens because `virt_machine_class_init()` in `hw/arm/virt.c` never gets called in that case, which means it doesn't initialize `mc->kvm_type` to the correct callback to do the IPA check.

Since the max IPA size is a property of the host CPU and must be queried properly for things to work at all, this logic should be invoked unconditionally for all machines, even `none`.

This is breaking libvirt on Apple M1/M2 systems, since it uses `-M none,accel=kvm` for its KVM test, and when it fails it considers KVM support unavailable. See: https://gitlab.com/libvirt/libvirt/-/issues/365
Steps to reproduce:
On any ARM64 machine:

1. strace -e ioctl qemu-system-aarch64 -M none,accel=kvm 2>&1 | grep -C1 CREATE_VM
2. strace -e ioctl qemu-system-aarch64 -M virt,accel=kvm 2>&1 | grep -C1 CREATE_VM

Observe that the first command line does not issue a `KVM_CAP_ARM_VM_IPA_SIZE` and does not set the machine type argument to `KVM_CREATE_VM`, while the second one does. On machines with <40 bit max IPA, the first invocation would fail to initialize KVM.