Re: qemu-kvm 0.12.3, Slackware 13 host and Windows XP guest - time drift a lot

[Zachary Amsden <zamsden@redhat.com>]

On 03/17/2010 09:22 AM, Thomas Løcke wrote:
> Hey all,
>
> I'm working on moving from a mixture of physical servers and
> virtualized servers running on Virtualbox, to a pure KVM setup. But
> I'm having some problems with my Windows XP guests in my test-setup.
>
> This is the host I'm testing on:
>
> CPU: Intel(R) Core(TM)2 Duo CPU E8500 @ 3.16GHz
> RAM: 8GB
> 2x320GB WD SATA disks (one for host OS and one for KVM guest images)
> 2x1GBs Intel nics (bonded)
>
> Host OS is Slackware 13 with the following kernels: 2.6.29.6-huge,
> 2.6.29.6-generic, 2.6.33 and 2.6.33.1
>
> qemu-kvm is 0.12.3
>    

qemu's been changing a lot, might be best to build from the actual git 
repository, which is 0.12.50 now.

> My Linux guests works like a charm. When they boot up I do a single
> "ntpdate -b europe.pool.ntp.org" and after that the time stays in near
> perfect sync with the host, with no ntpd running on the guests. My
> Windows XP guests on the other hand drifts backwards in time,
> especially when there's load on the guest, for example when I'm
> copying a large file from my samba server to the Windows XP guest. The
> guest can easily lose 10 minutes while copying a 600MB file. Or if I
> start a few browsers and point them at some horrible flash heavy sites
> and just let them sit there, then the VM also start losing a lot of
> time real fast.
>    

What's your host CPU load get up to.  You only have a single core?

> This is the commandline I use to start the Windows XP guests:
>
> qemu-system-x86_64 -hda winxppro.raw -boot c -m 1024 -vnc :1 -k da
> -smp 1 -localtime -daemonize -name qemu_winxppro,process=qemu_winxppro
> -net nic,macaddr=de:ad:be:ef:00:01,model=rtl8139 -net tap -runas kvm
>
> I use the same commandline for my Linux guests, except the nic is virtio.
>
> I'm at my wits end. I've tried the -tdf option with no success. I've
> tried setting various -rtc options with no success.
>    

Including -rtc-td-hack ?
> Could it be I'm missing some key-component in the kernel? Or is there
> perhaps some dev version of qemu-kvm I could/should try?
>
> According to some of the #kvm residents, this should "just work" (tm),
> but I simply cannot make it happen.
>
> Any and all advice are more than welcome.
>    

As always, make sure you are running the latest and greatest modules, 
those matter even more than the kernel, and check for any warning 
messages in dmesg and qemu output.

Zach