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From Eric Lee Green <>
Subject Re: Windows 10 KVM becoming inaccessible
Date Mon, 10 Aug 2020 01:04:48 GMT
I will note that we have several Windows 10 / Windows 2018 genre VM's on 
Centos 7.8.2003 and are not seeing any guest freezes. But:

1) We are not using CPU host-passthrough.

2) We do have the QEMU Windows guest drivers installed in the VM's.

3) I am running Cloudstack 4.11.3. I tried upgrading to Cloudstack 
4.14.0 and the upgrade failed, the agent was unable to ssh into virtual 
routers to configure them.

That said, the version of Cloudstack should not matter, since all 
Cloudstack does is tell libvirtd to launch the VM. libvirtd handles 
everything from there. We are literally using the stock Centos 7.8 
libvirtd.conf as modified by the agent configurator.  I wonder if you 
are having a hardware problem on your new server, or if there is a Linux 
OS problem handling your new server. Use journalctl and see if you're 
seeing anything at the Linux OS level when a freeze happens, and check 
the qemu log files for the instance also, because normally libvirtd is 
quite reliable and Centos 7.8.2003 supports Windows 10 VM's just fine.

On 8/9/2020 8:48 AM, Rohit Yadav wrote:
> Hi Dave,
> I've not specifically worked with Windows guest VMs on KVM, but what you've described
is largely subject to a guest OS support by the hypervisor, in this case the specific libvirt/qemu/linux-kernel
version and any guest tools/drivers that must be installed inside the Windows guest VM. You've
yourself acknowledged that the issue is not seen in your older CentOS6 based environment.
> To rule out CloudStack (a) you may add or upgrade hosts in a cluster to use qemu-ev (enterprise
qemu release by CentOS SIG, i.e.
install the centos-release-qemu-ev pkg) or (b) you may add a new cluster with Ubuntu 18.04
KVM hosts and recreate your Windows VM setup. Or, it could be a specific Windows build or
requires additional drivers (such as
> Hope this helps.
> Regards.
> ________________________________
> From: Dave Lapointe <>
> Sent: Saturday, August 8, 2020 00:48
> To: <>
> Subject: Windows 10 KVM becoming inaccessible
> Hi,
> I've been lurking on this group for a few years now and have found the information that
people have posted here to be quite helpful for me to understand CloudStack better.  I've
never replied here because there are always far more knowledgeable people on this list who
can offer much better insight than I ever could.
> An issue has arisen recently that I can't find any solution for.  I apologize ahead of
time if this is the wrong list to post to.
> I recently configured a new server to run CloudStack using Centos 7.8.2003 and CloudStack
4.14, and configured some Windows 10 LTSB KVM guests.  This is a fairly specialized server,
so the configuration is a little unusual.  It's configured to use the "cloudbr0" software
bridge for the guest network which is then routed externally through a single NIC.  Also,
because the VM's will never be migrated, I've set guest.cpu.mode=host-passthrough.
> What's been happening though is that the VM's will just freeze sometimes, apparently
randomly.  Sometimes it will happen during boot, or a couple minutes after connecting by RDP.
 And sometimes the VM won't freeze at all.  I haven't been able to determine a pattern as
to when this will happen.  And I haven't found anything in the logs that might help me understand
what's happening (/var/log/messages and /var/log/cloudstack/management/management-server.log).
 I've checked on the QEMU and Linux forums, but have only found a bit of information about
VM's freezing for people using specific graphics drivers with passthrough for their graphics
cards.  I tried removing guest.cpu.mode=host-passthrough but that made no difference.
> What's especially odd to me is that this didn't happen with older systems I've created
(eg. CentOS 6 and CloudStack 4.9).  I've setup half a dozen or so using the same configuration
as this system, just older software.
> I can't tell if this is related to CloudStack (maybe there is something in the guest
parameters that is causing this), or if this is strictly a KVM issue.  And since I can't find
anything in the logs I don't know where else to look.  I'm hoping to get some suggestions
from this list so that I can do some more digging.
> Thanks,
> Dave
> 3 London Bridge Street,  3rd floor, News Building, London  SE1 9SGUK
> @shapeblue

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