Important Hotfixes for Hyper-V on Windows Server 2008 R2 [reminder]

Important Hotfixes for Hyper-V on Windows Server 2008 R2 [reminder]

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Last week I received the latest support call statistics for Hyper-V on Windows Server 2008 R2 – and it seems that a number of you are hitting problems that we know about – and have hotfixes “ready to go” for.  So I would like to take a moment to bring these hotfixes to your attention. 

The first three are system crashes that are caused by processor erratum that were discovered after Hyper-V on Windows Server 2008 R2 shipped:

KB Number: KB975530
Title:Stop error message on an Intel Xeon 5500 series processor-based computer that is running Windows Server 2008 R2 and that has the Hyper-V role installed: "0x00000101 - CLOCK_WATCHDOG_TIMEOUT"
Description:This is fairly simple.  If you have a computer with an Intel Xeon 5500 series processor or an Intel Core-i series processor and you see this blue screen – install this hotfix.
Extra detail: I blogged about this back in October.  Some of you reported that this did not solve the problem for you.  The hotfix has since been updated to address the problem on these systems that were missed with the original fix.

KB Number: KB981791
Title:"STOP: 0x0000001a" error message on a computer that has an Intel Westmere processor together with the Hyper-V role installed on Windows Server 2008 SP2 or on Windows Server 2008 R2
Description: Once again, if you have this processor (Intel Westmere) and see this blue screen – get this hotfix.

KB Number: KB981618
Title: The computer stops responding or restarts during the Hyper-V Live Migration process in Windows Server 2008 R2
Description: This issue only affects AMD K10 processors, but otherwise is fairly straight forward.  It can actually also occur any time a virtual machine is saved / restored – but is much less likely to happen in those situations.

The next two hotfixes are ones that cause problems with networking performance / connectivity when the computer is under high load:

KB Number: KB974909
Title: The network connection of a running Hyper-V virtual machine is lost under heavy outgoing network traffic on a Windows Server 2008 R2-based computer
Description:This affects all guest operating systems.  The fix is applied to the hypervisor and while a reboot is required for installation, no updated need to be applied to the guest operating systems.

KB Number: KB981836
Title: Network connectivity for a Windows Server 2003-based Hyper-V virtual machine is lost temporarily in Windows Server 2008 R2
Description:This problem only affects Windows Server 2003 virtual machines.  After you apply the hotfix to the management operating system – you then need to upgrade the integration services for each of the Windows Server 2003 virtual machines.

One final note: many people have contacted me to ask how to actually get these hotfixes.  You do not need to call up Microsoft product support – but can get them directly from the above web pages by clicking on the “View and request hotfix downloads” link in each page – as shown here:



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  • For the WATCHDOG_TIMEOUT stop error. I have 2 Dell R710 experiencing this bug. By updating the lattest BIOS it seems to be gone for one of them and disabling C states completely in the BIOS seems working fine so far. Since this is a hotfix, I wonder if there is any schedule for a service pack soon? I would prefer service pack over hotfix. Another problem I encountered earlier is probably due to a bug in the Intel NIC driver. I am always using the latest one but it won't help. My workaround is to disable TCP offload on the Intel NIC.

  • Are these not distributed via Microsoft Update/WSUS then?

  • Thanks for detailing these all in one place.

    Any details if all of these fixes are included in SP1?

  • Brian Doré -

    Yes, these will be included in SP1.

    OtherKevin -

    No, in order for a hotfix to be distributed by Windows Update it has to impact a large number of users (of the total Windows user base) and while this affects a fair number of Hyper-V users, it does not (yet) meet the bar for Windows Update.

    william -

    There is no (official) ETA for SP1 at this point in time.



  • Ben

    First off, great blog. I've found way more useful info here than on some MS sites I could mention.

    Thanks for bringing these hotfixes to light. I have a fileserver VM (2008 R2) that kept dropping off the domain. I've applied KB974909 to my 2 hyper-v cluster nodes and haven't seen this behaviour in the VM since. I'd been scratching my head wondering what I'd misconfigured in my environment until I read this post.

    Which leads me to thinking, is there a list of hyper-v hotfixes anywhere on the web? If so we could scan this first when we hit issues to make sure we don't waste time (in my case two weeks) pondering what we might have done wrong!

    many thanks

    Michael Warren (UK)

  • @Michael:

    You could use these feed url from technet:

  • @Thomas

    Many thanks, I had already found but not noticed the RSS feed.


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