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[Qemu-devel] Re: [PATCH] re-set rtc date on reset handler
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH] re-set rtc date on reset handler |
Date: |
Tue, 08 Sep 2009 18:15:12 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Blue Swirl wrote:
> On Tue, Sep 1, 2009 at 7:22 PM, Glauber Costa<address@hidden> 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.
Ah, that looks like a useful approach! We currently face the issue of
vRTC drifting away from the host time (as the latter is tuned by NTP).
Do you or anyone else know if switching the PC RTC over to the scheme
used in the m48t59 may have some downsides? If not, I would happily hack
up a patch ASAP and suggest it for mainline.
Jan
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
- [Qemu-devel] [PATCH] re-set rtc date on reset handler, Glauber Costa, 2009/09/01
- Re: [Qemu-devel] [PATCH] re-set rtc date on reset handler, Blue Swirl, 2009/09/01
- Re: [Qemu-devel] [PATCH] re-set rtc date on reset handler, Glauber Costa, 2009/09/01
- [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler,
Jan Kiszka <=
- [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Jan Kiszka, 2009/09/08
- [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Jan Kiszka, 2009/09/08
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Dor Laor, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Jan Kiszka, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Avi Kivity, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Jan Kiszka, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Avi Kivity, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Anthony Liguori, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Gleb Natapov, 2009/09/09
- Re: [Qemu-devel] Re: [PATCH] re-set rtc date on reset handler, Anthony Liguori, 2009/09/09