The offset to add to the hosts monotonic time, kvmclock_offset, is calculated against the monotonic time at KVM_SET_CLOCK ioctl time. Request a master clock update at this time, to reduce a potentially unbounded difference between the values of the masterclock and the clock value used to calculate kvmclock_offset. Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> Index: linux-2.6-kvmclock-fixes/arch/x86/kvm/x86.c =================================================================== --- linux-2.6-kvmclock-fixes.orig/arch/x86/kvm/x86.c +++ linux-2.6-kvmclock-fixes/arch/x86/kvm/x86.c @@ -3806,6 +3806,7 @@ long kvm_arch_vm_ioctl(struct file *filp delta = user_ns.clock - now_ns; local_irq_enable(); kvm->arch.kvmclock_offset = delta; + kvm_gen_update_masterclock(kvm); break; } case KVM_GET_CLOCK: { -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html