CDOS ps/2 mouse problem

Qemu v2.10.2 (also tested with 2.11.0)
Host OS : CentOS 7 x86_64 (1708)
Guest OS : Concurrent DOS 386 3.0 (with GEM)

There is my launch command : 
/usr/local/bin/qemu-system-i386 -m 4m -cpu 486 -hda /home/my_user/HDD.img -vga std

When I'm launching the guest, it is not responding after focusing in the viewer. I think this is due to the ps/2 emulation because when I add "-usb -device usb-mouse" in my command I don't have this issue (but in this case, mouse is not supported by CDOS).

I tested with an older version of Qemu (0.11) which uses the Bochs bios (instead of SeaBios in newer versions), and I don't have this issue either.