linux-kernel - linux-3.2.1 + KVM: TSC unstable on Core i5-2400S / H67

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Date:	Tue, 24 Jan 2012 12:36:08 +0100
From:	Johannes Stezenbach <js@...21.net>
To:	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: linux-3.2.1 + KVM: TSC unstable on Core i5-2400S / H67

Hi,

I just got the following in dmesg with linux-3.2.1:

[23379.612251] usb 2-1.2: new high-speed USB device number 6 using ehci_hcd
[    0.006666] Marking TSC unstable due to KVM discovered backwards TSC
[23421.511167] Switching to clocksource hpet

The mainboard is an Asus P8H67-V, BIOS 0806 10/26/2011 with Core i5-2400S.
The kvm instance was running for a day already, and there was an overnight
suspend-to-disk cycle in between, but the above happened ~1 hour after resume.
(I don't think the usb message has anything to do with it, it's just
the last message before the TSC message.)

Hm, checking /var/log/kern.* it seems this also happened with
linux-3.1.* without me noticing.

Should I be worried?  I thought Core-i5 processors have a stable TSC?

Johannes
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