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Re: [Qemu-devel] Clock runs at double speed in guest


From: C.W. Betts
Subject: Re: [Qemu-devel] Clock runs at double speed in guest
Date: Sat, 31 Mar 2007 16:17:18 -0600

What OS are you using?
----- Original Message ----- 
From: "Thomas Tuttle" <address@hidden>
To: <address@hidden>
Sent: Wednesday, March 28, 2007 6:54 PM
Subject: [Qemu-devel] Clock runs at double speed in guest
>Hi.
>
> I have a 64-bit dual-core (Core 2 Duo) laptop, and I'm trying to install
> Gentoo AMD64 on a Qemu virtual machine.
>
> The system clock runs at double speed.  If I run `date' in a tight loop,
> I can see it ticking off two seconds for every one second of real time.
> The hardware clock does not run at double speed; if I run `hwclock
> --hctosys', the system clock jumps back to the right time.
>
> I have tried:
>
> 1) Setting the host's RTC's max-user-freq to 1024
> 2) Setting the guest's RTC's max-user-freq to 1024, just for good measure
> 3) Running the host with the CPU frequency locked to the minimum (1 GHz)
> 4) Running the host with the CPU frequency locked to the maximum (2 GHz)
>
> This problem does not occur if:
>
> 1) The guest is booted with the kernel parameter "nolapic"
> 2) The guest is a 32-bit kernel
> 3) I manually modify hw/mc146818rtc.c to send interrupts half as
>   often.
>
> I'd really like to get this fixed, because it's the only barrier to me
> being able to use Qemu (and KVM) for arch testing Gentoo.
>
> If there's any more information I can provide (if you need access to the
> machine, it could be arranged), please don't hesitate to ask.
>
> I am not subscribed to qemu-devel, so please CC me on replies.
>
> Thanks,
>
> Thomas Tuttle






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