Bug#839627: linux-image-4.7.0-1-amd64: kvm-clock provides unadjusted time

[Gedalya <gedalya@gedalya.net>]

On 10/06/2016 08:55 PM, Ben Hutchings wrote:

> Presumably you consider the behaviour on 4.6/4.7 to be undesirable.
>
>  From what I can see, the host side may attempt to keep the pvclock
> synchronised with its real time but it is not recommended for guests to
> rely on this.

It looked like an interesting change in behavior. From what I've read on 
this
topic, I know enough to always run ntpd in virtual machines, including KVM.

> check that the host is sending clock updates to the guest.

# cat /sys/module/kvm/parameters/kvmclock_periodic_sync
Y

# cat trace_pipe
    kworker/0:47-13195 [000] .... 387173.146166: kvmclock_update_fn 
<-process_one_work
    kworker/0:47-13195 [000] .... 387173.146174: kvmclock_update_fn 
<-process_one_work
    kworker/0:47-13195 [000] .... 387175.194257: kvmclock_update_fn 
<-process_one_work
   kworker/2:126-13231 [002] .... 387175.194260: kvmclock_update_fn 
<-process_one_work
    kworker/1:45-13244 [001] .... 387175.194263: kvmclock_update_fn 
<-process_one_work
   kworker/3:151-13105 [003] .... 387175.194265: kvmclock_update_fn 
<-process_one_work
    kworker/0:47-13195 [000] .... 387474.198723: kvmclock_update_fn 
<-process_one_work
    kworker/0:47-13195 [000] .... 387474.198735: kvmclock_update_fn 
<-process_one_work
    kworker/1:45-13244 [001] .... 387476.246874: kvmclock_update_fn 
<-process_one_work
   kworker/3:151-13105 [003] .... 387476.246879: kvmclock_update_fn 
<-process_one_work
   kworker/2:126-13231 [002] .... 387476.246883: kvmclock_update_fn 
<-process_one_work
    kworker/0:47-13195 [000] .... 387476.246884: kvmclock_update_fn 
<-process_one_work

Yet, the guests still seem to be getting the unadjusted time.


Thanks,

Gedalya