[Bug 98034] New: virt viewer QXL connection mouse unusable with >3ms latency with windows 8

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=98034

            Bug ID: 98034
           Summary: virt viewer QXL connection mouse unusable with >3ms
                    latency with windows 8
           Product: Spice
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: virt-viewer
          Assignee: spice-bugs at lists.freedesktop.org
          Reporter: andi-bz at firstfloor.org

This was originally in #91219, but it seems like a different problem, so I'm
opening a new bug.


I'm connecting with virt-viewer to a remote system running a qemu KVM VM with
Windows 8.1. There is some latency on the connection (not a LAN)

I installed QXL drivers in Windows 8.1.

When I don't use the QXL graphics, the mouse works fine, just the repaint
refresh is painfully slow (can watch it redraw)

When I use the QXL graphics, the graphics is faster. Everything  works fine
when I connect locally on the system to the VM using QXL.

However as soon as there is some latency on the QXL connection the mouse
pointer becomes unusable: the mouse pointer still moves, but doesn't react to
clicks anymore. When the latency becomes higher it doesn't even move anymore.

The non QXL connection doesn't have this problem, even at higher latencies the
mouse always works fine.

I did some experiments to characterize this: i'm running a FC23 guest on the
system with the Windows VM and use it to connect virt-viewer to the windows
guest running on the same host.

Initially the mouse works fine (latency low enough).

Then I add some extra latency on the guest with 
(this requires install kernel-modules-extra on FC23)

tc qdisc add dev ens3 root netem delay 5ms
...
tc qdisc del dev ens3 root netem  # needed to change the value

With 0ms extra delay the mouse click works fine.
With 1ms extra delay it gets slower, but is still usable.
With 3ms extra delay is barely reacts to mouse click anymore (but still moves)
Usually the first click still works, but then later clicks don't, so it seems
something is stuck in the protocol?
With longer delays the mouse pointer also stops moving, not just the clicks.

Other experiments tried:
- It is not the specific FC23 virt viewer version. I also used an older version
from OpenSUSE Leap, and also a very recent version from opensuse, and they also
had the same problem.


Versions: (FC23)

virt-viewer-3.0-1.fc23.x86_64
qemu-kvm-2.4.1-11.fc23.x86_64

The windows guest is running:

Windows 8.1
Red Hat QXL controller 17.54.59.923  4/21/2016

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