Control: severity -1 normal Control: tags -1 moreinfo I'm afraid I don't really know how to debug this. I think this is very probably a bug in the Linux kernel, and not a bug in Xen. Specifically, it's probably a bug in the nouveau driver. I'm not really qualified to debug it.
I'm downgrading this because I'm pretty sure it only affects people using this particular graphics driver. Also this bug is quite old. We have Xen 4.8 in stretch, and a newer version of Linux. So it may well be that the bug has been fixed. I'm going to leave this bug open for now but unless I get more reports like this, or a confirmation that the bug is still present in recent versions, I will probably close it at some point. Thanks, Ian.
