Forwarding from Debian bugreport http://bugs.debian.org/922612
18.02.2019 15:43, Marc Lehmann wrote:
Package: qemu-system Version: 1:3.1+dfsg-4 Severity: normal Dear Maintainer, after upgrading to qemu 3.1 from stretch [from qemu 2.8 -- mjt], I found that both linux and windows guests, when using the qxl device, do not come back from deep power save. That is, when I run either a standard ubuntu 17.10 or windows 10 (with qxl-dod driver), then by default they switch off the screen after a while, which results in black screen in qemu, as expected. If one moves the mouse or presses a key shortly after this, the screen comes back. If I let the systems idle for longer (say, half an hour), then they seem to go into a deeper powersave, and pressing a key or moving the mouse does NOT restore the screen - it stays black. When the vm is in this state, I have not found a way to get the display back, the only way that works is to quit qemu and start it again (meaning boot the guest again in a new qemu instance, I have not tried to suspend/resume a vm). I have verified that mouse inputs and keypresses are registered correctly by the guest in this state, so I assume it does try to switch on the virtual monitor. Since this happens with both linux and windows guests, this looks like a bug in qemu's display code to me.
Thanks, /mjt
