On 11/01/2017 14:26, Eduardo Habkost wrote: > On Mon, Jan 09, 2017 at 03:58:11PM +0100, Paolo Bonzini wrote: >> >> >> On 08/01/2017 21:28, Eduardo Habkost wrote: >>>> Well just export KVM_GET_TSC_KHZ in a QMP command right? Its pretty >>>> easy. >>>> >>>> Let me know if you need any help coding or testing. >>> I just found out that KVM doesn't provide something that QEMU and >>> libvirt need: the value of kvm_max_guest_tsc_khz. Without it, we >>> have no way to know if a given VM is really migratable to a host. >>> >>> Could we add a KVM_CAP_MAX_TSC_KHZ capability for that? >> >> The ratio is really quite high, 256x the host frequency for AMD and >> 65536x for Intel. Anything below 2^32 Hz (above that, there would >> probably be other failures) is safe. > > 2^32 Hz (~4.3 GHz) sounds like a limit likely to be hit by future > CPUs. Which kind of failures do you think we could see? Just integer overflows. Current CPUs have been at 3.9 GHz for a while now. Paolo -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
