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From: Blue Swirl <blauwirbel@gmail.com>
Date: Tue, 1 Sep 2009 19:56:56 +0300
Message-ID: <f43fc5580909010956l5f4b8ea1p47bf85811a4f858a@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH] re-set rtc date on reset handler
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To: Glauber Costa <glommer@redhat.com>
Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org

On Tue, Sep 1, 2009 at 7:22 PM, Glauber Costa<glommer@redhat.com> wrote:
> guests without a stable timesource such as kvm-clock will grab the wallclock
> from our rtc chip. However, we only sync the date when we first launch qemu.
> If a guest goes through a series of reboot cycles, it will slowly see time
> getting far behind the host.
>
> The proposal of this patch is to set the date to host clock again in the reset
> handler. With this patch, I see a Fedora guest keeping its clock in sync upon
> an ulimited number of reboots.

A different approach is used in m48t59.c: the guest clock is generated
directly from host clock without any timers and only a fixed offset
(to account for time when guest was stopped) is added, so the clock
will always in sync.