2017-06-12 21:23+0800, Jay Zhou: > Guest using kvmclock will be hanged when migrating from unstable > tsc host to stable tsc host occasionally. > Sometimes, the tsc timestamp saved at the source side will be > backward when the guest stopped, and this value is transferred > to the destination side. The guest at the destination side thought > kvmclock is stable, so the protection mechanism against time > going backwards is not used. > When the first time vcpu0 enters the guest at the destination > side to update the wall clock, the result of > pvclock_clocksource_read will be backward occasionally, > which results in the wall clock drift. > > Signed-off-by: Jay Zhou <jianjay.zhou@xxxxxxxxxx> > --- Hm, are you using KVM that has e3fd9a93a12a (4.9+)? If you get a timestamp from KVM_GET_CLOCK() and pass that to KVM_SET_CLOCK(), then kvmclock should not jump backwards anymore (it could before 4.9, but only if the host had stable tsc). A possible source of this bug in when QEMU recomputes the timestamp to pass to KVM_SET_CLOCK() using TSC and kvmclock page. Can you provide the values used for KVM_GET_CLOCK and KVM_SET_CLOCK when the bug occurs? Thanks.
