[vfio-users] Host hard lockups

[Bronek Kozicki]

On 05/08/2016 22:11, vfio wrote:
> Hello everyone,
>
> I've been running VGA passthrough with a Debian unstable host and a
> Windows 10 guest for months now. Everything works perfectly, except that
> the entire machine randomly freezes when the guest is running.
>
> When a freeze happens, the guest immediately locks up. Sometimes, if
> audio was playing, it goes into a short loop. Strangely, the host does
> not usually freeze immediately; it takes a few seconds after the guest
> has frozen. For example, my CPU monitor on the host will usually perform
> a few more measurements before completely freezing, and the mouse cursor
> on the host machine will continue working for a few seconds as well.
>
> When the host freezes, not even the physical reset button on the machine
> works. It requires a hard reset by holding the power button. There have
> been a few times where the reset button worked. However, in one of these
> instances, the host refused to boot after a reset, claiming to be unable
> to initialize one of the USB buses. Sometimes the issue does not happen
> for several days with multiple-hour sessions. Sometimes it happens
> multiple times per day, possibly a few minutes after booting the guest.
>
> No freeze leaves any traces in syslog.
>
> These issues are very similar to those reported by Colin Godsey on this
> list in May. While the conclusion of that thread seemed to be BIOS
> firmware problems or "the Skylake freeze", I am using a Core i7-4960X
> (Ivy Bridge-E) and an ASUS Rampage IV Extreme with the final BIOS
> revision (4901 from 2014-06-18).


I had something similar too, it was happening few times per month. And 
then it stopped, but I do not remember what changed back then :( Could 
be hardware change since I switched around that time from AMD to nVidia 
Quadro, or could be software change as I upgraded to qemu 2.5 (but I see 
you are running 4.6, so probably not this). I also made changes in my 
system configuration to ensure it does not run out of RAM (it is also 
running ZFS, which is very greedy).


B.