Hi, since I cannot use kvm-clock as the clock source (older guest kernel) I am using pit as the clock source. According to my tests this is the most stable clock source among tsc,hpet but still can drift. Since the qemu keeps the /dev/rtc perfectly synchronized with the Host's system time it is a good time source for the ntpd on the guest. The host itself is then sychronized via NTP with the external time server. I don't know any other way how to read the system time from the Host, please offer if you have some.
The only disadvantage is that when the step time back must be done on the Host, the /dev/rtc gets stuck (it is a monotonic clock) and the qemu must be restarted. Regards Pavel > -----Original Message----- > From: unruh [mailto:un...@wormhole.physics.ubc.ca] > Sent: Tuesday, June 15, 2010 2:23 AM > To: questions@lists.ntp.org > Subject: Re: [ntp:questions] Reference clock driver for /dev/rtc > > On 2010-06-14, Krejci, Pavel > <pavel.kre...@siemens-enterprise.com> wrote: > > Hello, > > > > I have written the reference clock driver for /dev/rtc on > Linux. We use it to synchronize the guest Linux system > running in the qemu with the Host clock. If this is useful to > someone else I would like to contribute to the NTP project. > How should I proceed? > > > > Why would you want to do that? The rtc is almost certainly > worse than the system clock. Why not have the guest just read > the host's system clock, rather than the rtc. > > > > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
