Hello Ian, Am Mittwoch 11 Januar 2012 12:54:04 schrieb Ian Campbell:
On Wed, 2012-01-11 at 10:20 +0000, Philipp Hahn wrote:
I'm currently tracking a problem in libvirt regarding Xens handling of localtime and rtc_timeoffset. My current understanding (Xen-3.4.3 and Xen-4.1.2 under Linux) of Xend (the depcrecated Python one still used by libvirt) is as this: - for HV domains, the RTC gets setup to either UTC or localtime depending on "/domain/image/hvm/localtime" ± "/domain/image/hvm/rtc_offset".
Are those xenstore paths or a reference to a config file/sxp var?
Those are XenStore paths.
I don't see the string "rtc_offset" anywhere under tools in xen-unstable.
I missed the "time", it's "rtc_timeoffset". Best search for RegExp rtc.timeoffset, since so you'll find 'rtc/timeoffset' as well. ...
They get PV time direct from the hypervisor which exposes the hypervisor's wallclock to guests via the shared info. It is always UTC. See http://xenbits.xen.org/docs/unstable/hypercall/include,public,xen.h.html#St ruct_shared_info in particular the wc_* fields.
Yes, I figured that out as well, but thanks for the link.
Classic-Xen kernels by default will take wallclock time from the shared info for each gettimeofday but can be configured to be free-running (that is the "independent_wallclock" mode).
A lot of documentation still talks about /proc/xen/independent_wallclock, which doesn't exist in 2.6.32 any more. I wish they would mention the Xen version and Linux kerbel version they were using ... Thank you for your fast feedback. Sincerely Philipp Hahn -- Philipp Hahn Open Source Software Engineer hahn@univention.de Univention GmbH Linux for Your Business fon: +49 421 22 232- 0 Mary-Somerville-Str.1 D-28359 Bremen fax: +49 421 22 232-99 http://www.univention.de/