On Thu, 20 Jul 2023 at 08:29, Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote: > > libvirt uses "none" machine type to test KVM availability. Before this > change, QEMU used to pass 0 as machine type when calling KVM_CREATE_VM. > > The kernel documentation says: > > On arm64, the physical address size for a VM (IPA Size limit) is > > limited to 40bits by default. The limit can be configured if the host > > supports the extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use > > KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type > > identifier, where IPA_Bits is the maximum width of any physical > > address used by the VM. The IPA_Bits is encoded in bits[7-0] of the > > machine type identifier. > > > > e.g, to configure a guest to use 48bit physical address size:: > > > > vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48)); > > > > The requested size (IPA_Bits) must be: > > > > == ========================================================= > > 0 Implies default size, 40bits (for backward compatibility) > > N Implies N bits, where N is a positive integer such that, > > 32 <= N <= Host_IPA_Limit > > == ========================================================= > > > Host_IPA_Limit is the maximum possible value for IPA_Bits on the host > > and is dependent on the CPU capability and the kernel configuration. > > The limit can be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the > > KVM_CHECK_EXTENSION ioctl() at run-time. > > > > Creation of the VM will fail if the requested IPA size (whether it is > > implicit or explicit) is unsupported on the host. > https://docs.kernel.org/virt/kvm/api.html#kvm-create-vm > > So if Host_IPA_Limit < 40, such KVM_CREATE_VM will fail, and libvirt > incorrectly thinks KVM is not available. This actually happened on M2 > MacBook Air. > > Fix this by specifying 32 for IPA_Bits as any arm64 system should > support the value according to the documentation. > > Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> > --- > Resending due to inactivity. > > accel/kvm/kvm-all.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index 373d876c05..3bd362e346 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -2458,7 +2458,11 @@ static int kvm_init(MachineState *ms) > KVMState *s; > const KVMCapabilityInfo *missing_cap; > int ret; > +#ifdef TARGET_AARCH64 > + int type = 32; > +#else > int type = 0; > +#endif > uint64_t dirty_log_manual_caps; > > qemu_mutex_init(&kml_slots_lock); > -- > 2.41.0 I think this was discussed in review the last time around on this patch (which is why it wasn't applied), but I don't think we should do this with a target ifdef in a common file. We should have some kind of target hook for targets to specify what they need to do here. thanks -- PMM
