Re: [libvirt] [Xen-devel] [BUG, PATCH-RFC] libvirt localtime and rtc_timeoffset handling in xen-sexpr/sxpr/sxp
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(a)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/
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