RE: [Xen-users] Desynchronize clock

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Steve Brueckner
> Sent: 07 March 2007 18:11
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-users] Desynchronize clock
> 
> Petersson, Mats wrote:
> >> -----Original Message-----
> >> I don't want my dom0 to update the clock in my HVM domU.  I've
> >> already disabled network-based time synchronization inside the HVM.
> >> I've tried
> >> setting /proc/sys/xen/independent_wallclock=1 and then restarting
> >> xend, but the guest still gets the correct time.
> > 
> > Did you set independent wallclock in the guest or on Dom0? 
> You should
> > set it on guest, as that's "who" should have a different clock to
> > Dom0, right? It's a per-domain settings, so individual domains are
> > allowed to be either independent or "same".   
> > 
> 
> Ah, good point.  Unfortunately, the guest is Windows, so there is no 
> /proc/sys/xen/independent_wallclock setting inside the HVM.  What I 
> need is a way to tell domU which domains should be given 
> access to the 
> system or hardware clocks.

Yes, someone else pointed out that it was a HVM guest after I'd written
the reply (typical "did not read all of the important bit"). But
indpendent_wallclock is really a per-domain setting anyways, so it's not
really right to set it in Dom0. 


> 
> In a recent, related post, someone said that for HVMs, "Dom0 time has 
> no bearing to the guest's time."  However, every time I reboot the 
> Windows HVM it has the correct time.  Since I've disabled 
> network-based 
> time synch inside the Windows HVM, I have to assume it's getting the 
> time from either dom0's system clock or from the hardware 
> clock on the 
> motherboard, no?

Actually, I think the time is kept by the virtual CMOS and Timer
functionality in the HVM + QEMU-DM parts of Xen. 

You may be able to tweak those with some tools... I don't think the
tools exist today tho'. 

--
Mats
> 
> Steve Brueckner, ATC-NY
> 
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> 



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