I accidentally first sent this reply from a different email address, and am
resending with my correct email address. I apologize if the reply shows up
twice in the list.
Hello,
Thanks for this information. I think I may have stumbled on a solution
(stumble really is the operative word here). To follow up on the responses
though:
I've tried both with passthrough and without it, and the results were the same.
In my searching for a solution I found out about centos-release-qemu-ev and
installed qemu-ev. It didn't seem to change this behaviour, but it did appear
to reduce the host cpu with idle guests (although not as much as I'd hoped).
I used the latest virtio.iso from Fedora to install what drivers I could. Some
drivers wouldn't install though (eg. network and graphics)... I got messages
about version incompatibility, or configuration errors.
I decided to do a completely new install (O/S and CloudStack) on a different, much older machine,
and found that I had different behaviour. The VM's ran without any problems. Aside from the
hardware differences, I also used just the default "Medium" Compute Offering for the VM's
(which I think is 1GB RAM and 1GHz CPU). And this is where I stumbled on the solution. On the
problematic system, I had created a Compute Offering that I thought was suited to the hardware
configuration and the number of concurrent VM's that would run on it. So I switched the VM's to
the default "Medium" Compute Offering on this new computer. And the VM's didn't freeze.
I experimented with different Compute Offerings and found that this was what made the difference.
In this case, it looks like the Compute Offering's CPU speed has to be set somewhat lower than the
actual CPU speed. Adding cores to the Compute Offering with the lower CPU speed also worked.
I think this is just my lack of knowledge... I seemed to recall that QEMU
wouldn't start a VM with an incompatible configuration. But that may not be
the case, as this experience indicates. It's possible too that the
configuration wasn't incompatible but that it happened to be something that
caused Windows to not play nice because I had no issues with an Ubuntu Desktop
VM using the same Compute Offering.
Thanks for your help,
Dave
On 08-09-20 6:04 p.m., Eric Lee Green wrote:
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
https://wiki.centos.org/SpecialInterestGroup/Virtualization, 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
https://www.linux-kvm.org/page/WindowsGuestDrivers/Download_Drivers).
Hope this helps.
Regards.
________________________________
From: Dave Lapointe <[email protected]>
Sent: Saturday, August 8, 2020 00:48
To: [email protected] <[email protected]>
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
[email protected]
www.shapeblue.com
3 London Bridge Street, 3rd floor, News Building, London SE1 9SGUK
@shapeblue
