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[Xen-devel] Re: [PATCH] [PVOPS] dom0 sync xen wallclock

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] [PVOPS] dom0 sync xen wallclock
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Fri, 19 Feb 2010 09:10:50 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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On Thu, 2010-02-18 at 23:43 +0000, Jeremy Fitzhardinge wrote:
>     * PV domUs get a rough time of day at boot either from a simple
>       "seconds since 1970" in the startup info put there by the domain
>       builder from dom0's clock (so there's no illusion that it is
>       anything other than a one-time start time for the domain)

Unfortunately there is an existing large installed base of guests which
use the dependent wallclock mode since it is the default in oldstyle Xen
kernels.

>     * HVM domains similarly get an emulated CMOS implemented in qemu 

Isn't this currently emulated within the hypervisor using the wallclock
time within Xen? I assume that it was pulled into the h/v for a specific
reason? I'm not sure what reason though, the emulated RTC doesn't seem
especially performance critical...

Ian.


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