* Re: [Qemu-devel] [patch 0/2] add QMP command to reset rtc interrupt backlog [not found] <20140530140523.653892288@amt.cnet> @ 2014-06-02 9:13 ` Michal Privoznik 2014-06-02 16:31 ` Marcelo Tosatti 0 siblings, 1 reply; 2+ messages in thread From: Michal Privoznik @ 2014-06-02 9:13 UTC (permalink / raw) To: Marcelo Tosatti, qemu-devel; +Cc: gleb, pbonzini, armbru On 30.05.2014 16:05, Marcelo Tosatti wrote: > It is necessary to reset RTC interrupt backlog if guest time is > synchronized via a different mechanism, such as QGA's guest-set-time > command. > > Failing to do so causes both corrections to be applied (summed), > resulting in an incorrect guest time. > > Marcelo, what happens if quest is synchronized via NTP? Does this command still need to be executed after 'cont'? Michal ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [patch 0/2] add QMP command to reset rtc interrupt backlog 2014-06-02 9:13 ` [Qemu-devel] [patch 0/2] add QMP command to reset rtc interrupt backlog Michal Privoznik @ 2014-06-02 16:31 ` Marcelo Tosatti 0 siblings, 0 replies; 2+ messages in thread From: Marcelo Tosatti @ 2014-06-02 16:31 UTC (permalink / raw) To: Michal Privoznik; +Cc: gleb, pbonzini, qemu-devel, armbru On Mon, Jun 02, 2014 at 11:13:15AM +0200, Michal Privoznik wrote: > On 30.05.2014 16:05, Marcelo Tosatti wrote: > >It is necessary to reset RTC interrupt backlog if guest time is > >synchronized via a different mechanism, such as QGA's guest-set-time > >command. > > > >Failing to do so causes both corrections to be applied (summed), > >resulting in an incorrect guest time. > > > > > > Marcelo, > > what happens if quest is synchronized via NTP? Does this command > still need to be executed after 'cont'? > > Michal Yes because NTP will either take time to adjust by slewing or step the clock (which renders guest-set-time() unuseable). During that time, guest clock will be ahead of realtime. Algorithm should be: - ret = guest-set-time() - if (ret = success) - rtc-reset-reinjection() That leaves a window where RTC interrupts are reinjected, but i see no better option. ^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2014-06-02 16:32 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
[not found] <20140530140523.653892288@amt.cnet>
2014-06-02 9:13 ` [Qemu-devel] [patch 0/2] add QMP command to reset rtc interrupt backlog Michal Privoznik
2014-06-02 16:31 ` Marcelo Tosatti
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).