First of all, AFAIR, all power events are logged into dmesg. And also i've had a similiar behaviour when the guest has some kind of a glitch and there is an interrupt storm happening. It can be observed via guest windows task manager(system interrupts task takes a lot of cpu) or on host by watching /proc/interrupts. And the last idea i have is to observe lspci when everything's fine and when the supposed low power mode happens. <div class="gmail_quote">On Nov 17, 2015 6:13 AM, "Eric Hattemer" <<a href="mailto:hattenator@gmail.com">hattenator@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">So I have this weird issue where if I run my Windows guest for days in a row, without allowing it to blank the screen or suspend or hibernate, it runs at full performance. If I suspend it and let Linux blank the screen, or let Windows blank the screen, or things of that nature, it tends to break forever. That is, rebooting Windows or starting a fresh qemu process (that doesn't resume from hibernate) doesn't fix anything. The symptom is that the VM functions at about 1/10th speed. It takes 10x as long to boot. Dragging windows across the screen stutters. The sound playing almost refuses to work. Rebooting the host (Linux) makes everything work again until it has a chance to enter low power mode or whatever. It's probably either the sound card or more likely the Nvidia 660 that's causing the problem, since those are both vfio-pci redirected. I fixed it once without rebooting by messing with all of: modprobe -r vfio-pci service acpid restart tuned-adm profile powersaving tuned-adm profile vm-host modprobe nouveau modprobe -r nouveau modprobe vfio-pci and maybe some rescanning/disabling/enabling or things in /sys/bus/pci... I'm really not sure how I did that and I haven't really been able to fix it without a reboot since. The important thing to note about modprobing nouveau is that the sysfs node for the video card still had driver_override=vfio-pci. Otherwise nouveau really does take it over and there doesn't seem to be a way to unload nouveau once it's attached to a card. I ran MSI afterburner in the guest to look at the GPU clocks and see if I could get it to re-activate them to full speed. But it might not really be a clocking issue, since I see about the same graphs whether the issue is present or not. Maybe my hypothesis that this is GPU power-saving related is wrong, but everything seems to run full speed if I disable vfio and run with the spice graphics card. So I'm wondering what exactly would cause this and what I should do to avoid/fix it. I'm not that familiar with low-power modes and how they're managed. Is this something well-understood, or am I the only one having this problem? -Eric Hattemer _______________________________________________ vfio-users mailing list <a href="mailto:vfio-users@redhat.com" target="_blank">vfio-users@redhat.com</a> <a href="https://www.redhat.com/mailman/listinfo/vfio-users" rel="noreferrer" target="_blank">https://www.redhat.com/mailman/listinfo/vfio-users</a> </blockquote></div>