== SRU Justification ==
The bug reporter states that after upgrading his laptop to Ubuntu 17.10, he was
unable to access gettys on any of the text-mode VTs on his system.
gdm3 is running on VT1, his user session is running on VT2. He could switch
between these. If he switched to VT3, the display retained the output of
his X session, and the text console with getty never appears. Switching
back to VT2 works fine.
The same problem was occuring with either Wayland or X.
This bug is a regression in Artful introduced by mainline commit:
7581d5ca2bb ("drm/i915/fbdev: Check for existence of ifbdev->vma before operations").
It was first found that this bug was fixed in v4.14-rc1. However, after a lengthy
"Reverse" bisect, the exact commit could not be identified. This is because the
fix came in via a merge base. A regular bisect was then done to identify commit
7581d5ca2bb as the offending commit that introduced the bug. Using the file
that this commit touched, a "Reverse" bisect was done again between
7581d5ca2bb..v4.14-rc1. This identified the following commit 88be58be886f as
the fix to this regression.