[clug] KVM & Virt-Manager

Rodney Peters rodneyp at iinet.net.au
Wed Apr 13 05:22:42 UTC 2016

On Tuesday 12 Apr 2016 21:44:25 George at Clug wrote:
>     Does anyone use KVM and Virt-Manager to host Guest VMs on their
> Linux desktop computer?   I have been for the past six or so months.
> I ha​ve found that KVM as a Hypervisor works quite well. However
> when I create a Cinnamon Guest and log in, the system reports "Running
> in software rendering mode", "Cinnamon is currently running without
> video hardware acceleration and, as a result, you may observe much
> higher than normal CPU usage".
> Now I suspect few people bother to run guest VMs with a Desktop
> Environment, and in particularly with Cinnamon or with Gnome. 
> Hopefully though there will be at least a few people who do (or at
> least have tried).
> As per one of my previous emails, VMware Workstation can emulate video
> hardware acceleration good enough for Cinnamon to believe it is
> running on true hardware.
> Searching the Internet I have found reports that suggest this is not
> currently possible, some reports suggest it is with virgil3d, but as
> yet this project is not packaged with Debian as yet, and then there
> are reports of "gl='yes'" and "accel3d='yes' accel2d='yes".
> https://en.wikipedia.org/wiki/Kernel-based_Virtual_Machine
> "Video card [1] Cirrus CLGD 5446 PCI VGA card, dummy VGA card with
> Bochs [2] VESA [3] extensions, or Virgil [4] as a virtual 3D GPU"
> I have tested the below two configurations for my test Guest VM, but
> they do not appear to work the way I expect them. Have you any
> experience with these settings and knowledge of what they actually do,
> and any conditions (hardware or software) that must be met for them to
> be used, please do let us know.
> If you do not understand why I want to run a Cinnamon Linux
> installation as a guest VM, do not worry, it is just a particular idea
> that I have for testing various GUIs (i.e. Desktop Environments
> without needing separate physical computers.
> Regards, George.
Hi George,

Although I use kvm routinely for various purposes - testing new disto, 
alternative desktops & packages, well as providing help with distro I don't 
routinely use (such as anybuntu) the default emulated graphics is adequate for 
my purposes.

kvm relies on using desktop RAM as video RAM plus a VNC type link to transmit 
to the real screen, both of which one would expect to throttle 3D performance.  

I use openSUSE host, which defaults to "Spice" as the VNC plus QXL (in lieu 
Cirrus) as the video card.   The wikipedia article that you cite suggests that 
those are the best performing video combination available.

As a first test you, are you able to simply change the settings for virtual 
machine details in your clients to those ?

If performance were still not adequate they you could try transmitting real 3D 
graphics over a VNC to another real PC and see if it is much chop anyway. 


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