Re: video/GPU passthrough, second monitor, shared keyboard/mouse

[Daniel Pocock <daniel@pocock.pro>]

On 29/07/15 20:41, Alex Williamson wrote:
> On Wed, 2015-07-29 at 12:59 +0200, Daniel Pocock wrote:
>>
>> Hi all,
>>
>> I'm looking at a setup that involves a Linux host and a non-Linux VM
>> under KVM, on a workstation for a power-user.
>>
>> The non-Linux VM would have a dedicated video card/GPU, to maximize
>> compatibility and performance for certain applications.
>>
>> It may be possible to interact with the VM using SPICE but it is
>> possible to just have a second monitor for it too.
>>
>> So my questions are:
>>
>> - Does all this make sense?
> 
> Yes, though your last point about using spice is a bit off.  With an
> assigned GPU, the content of the display is owned by the guest, the
> spice server in the host does not have access to it.  The spice
> connection is therefore limited to any emulated graphics that may also
> be attached to the VM.  It's possible to mirror the display between
> physical and emulated graphics, if the guest supports it, but
> performance will suffer substantially.  It's best to consider only
> guest-based remote access mechanisms for GPU assignment VMs (ex.
> guest-based VNC server).
> 

I wasn't really thinking about spice for graphics, I was just thinking
about whether the spice protocol would provide a means for sending
keyboard and mouse controls from the host to the VM

In other words, instead of using x2vnc, is there something like x2spice
or is it theoretically possible for such a thing to be created and would
it have any benefit over using x2vnc?

>> - How to share the keyboard and mouse between the host and the VM?  E.g.
>> should I just use Synergy or x2vnc or is there a nicer solution with KVM
>> or qemu?
> 
> Synergy works.  Any mechanism you would use to control a separate
> physical system works.  It's also possible to assign a USB controller to
> the VM and use a KVM switch between host and guest as well.  USB
> "passthrough" (vs assignment) is also possible for individual USB
> endpoints.
>

I have a preference for a software solution like Synergy or x2vnc.
Somebody on another list commented that he wasn't satisfied with
Synergy, are there any serious limitations or have there been in the past?

>> - are any other free software solutions (e.g. VirtualBox, Xen) likely to
>> be better or worse for such a project?
> 
> You're asking this to the kvm list, obviously we want kvm to be the best
> solution for this.  Thanks,
>

I had seen a few web pages suggesting that KVM offers better passthrough
support but VirtualBox or VMWare offer better emulated 3D graphics
within the VM at present (for people who don't have a second video
card/display).  Is that still the case or KVM can now provide some kind
of emulation of a display adapter with 3D acceleration?

Another issue with passthrough: is it OK to suspend and restore when the
video card is configured this way?  VirtualBox's passthrough
documentation says they don't support suspend for VMs using PCI passthrough.

Regards,

Daniel