On Mon, Apr 09, 2018 at 11:00:06AM -0600, Chris Friesen wrote: > Hi, Hi Chris, > I was looking at the patch series at > "https://lkml.org/lkml/2017/1/24/551"; and I had a few questions. > > First, did this or something like it ever get merged? Yes it was. Instructions to setup can be found at: https://opensource.com/article/17/6/timekeeping-linux-vms (At the end of the article). > Second, is something like this always needed with KVM, or does it > depend on how the guest keeps track of time? Only to keep very accurate time between guest and host (depends on the load of the system), but below 10us in a synthetic test-case. In case, for example, the host is PTP synchronized via network. For most use-cases NTP synchronization via network is sufficient. > From a purely theoretical point of view it seems like it should be > possible to adjust the time reported by the virtual/paravirtual > clock sources such that the guest would always see the "correct" > time as long as the host is keeping "correct" time. > > Thanks, > Chris Friesen This KVM PTP driver keeps the difference below the host clock and guest clock maxed at 10us.
