[Qemu-discuss] Mouse cursor sometimes can't pass the invisible border on the right side of the screen

[Mikhail Akushsky]

Hi,

I'm using qemu 2.11 on Gentoo Linux, with configured GPU passthrough
(Radeon RX580) to the guest Windows 10.
This configuration is alive for last 4 years, this time I changed a lot
qemu, linux kernel and windows versions, changed GPU and always all was
working as expected. I always used standard PS/2 mouse emulation and
that was enough for me.

Now, I bought two new monitors, instead of old one, and setup them as
one logical monitor, using technology called Eyefinity - it's a part of
standard Radeon software. Now Windows thinks, that I have one monitor
with resolution 2160x1920 (I bought Dell monitors with a thin borders
and use them in portrait mode).

Windows uses it without any problems, but mouse become crazy - sometimes
(~3 times from each 5) I can't move cursor to the right border of the
screen, it looks like the invisible vertical border. I spent really huge
amount of time to understand, which component is the root of problem and
found, that it's really a mouse. I tried all possible variants
(standard, tablet, virtio-mouse-pci, virtio-tablet-pci), and found, that
in both mouse variants bug is reproducing, and in both tablet variants -
cursor stuck near all real borders and corners, so it's not a variant too.
The only working variant becomes passing real USB port to my VM and
insert second mouse to this port. So, now it's working, but I have two
mice on my working place, which doesn't seems very useful.

Here is my command line:

QEMU_AUDIO_DRV=pa QEMU_PA_SAMPLES=4096 qemu-system-x86_64 -enable-kvm -M
q35 -m 12168 -cpu host,kvm=off -smp 4,sockets=1,cores=4 \
-bios /usr/share/qemu/bios.bin -rtc base=localtime -vga none -device
secondary-vga \
-drive
id=virtiocd,if=none,format=raw,file=/home/akushsky/virtio-win-0.1.141.iso \
-device driver=ide-cd,bus=ide.1,drive=virtiocd \
-device
ioh3420,bus=pcie.0,addr=1c.0,multifunction=on,port=1,chassis=1,id=root.1 \
-device
vfio-pci,host=05:00.0,bus=root.1,addr=00.0,multifunction=on,romfile=/opt/kvm/images/Sapphire.RX580.8192.170320_1.bin,x-vga=on
\
-device virtio-scsi-pci,id=scsi \
-drive
file=/dev/sdb,id=disk,format=raw,if=none,discard=on,cache=none,aio=native,detect-zeroes=unmap
-device scsi-hd,drive=disk,id=scsi0 \
-device ich9-intel-hda,bus=pcie.0,addr=1b.0,id=sound0 -device
hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 \
-usb -usbdevice host:046d:c52b

All in all, I checked on Windows 7 and Windows 10, and on qemu 2.10 and
2.11 - bug is always reproducible.

Also it's described here in bugreport:
https://bugs.launchpad.net/qemu/+bug/1750899


Best regards, Michael Akushsky.