Radeon VM Fault crash with Unreal Engine 4.17

Hi,
Well first I am not really sure if this is the right place to talk 
about this but the mailing list says "Newbie questions are OK".
A few days ago I tried to install Unreal Engine 4.17 on a carrizo APU 
and I got a instant freeze of the PC (using amdgpu driver) and today I 
tried the same UE4.17 with a Cape Verde GPU with a radeon driver. After 
talking a bit with awesome guys on #UE4Linux I could finally got more 
info than "it freeze" (run ./UE4Editor with -NOSPLASH) and it seems 
that the kernel land driver is crashing.
Here is my dmesg:
pastebin.com/raw/aM12R49K
my cat /var/log/Xorg.0.log | grep EE look like this:
pastebin.com/raw/m33JZ19n

I have found some bugs with a bit similar symptoms like this one: 
bugs.freedesktop.org/show_bug.cgi?id=101977 but nothing exactly like my 
problem (which is weird because I can reproduce it excactly on two 
different PC)
I am using Gentoo 4.12.4 with mesa 17.1.5, llvm 4.0.1 and X11 1.19.3.
Should I report this bug ? Is it already a known bug and I missed the 
related bug-traker post ?
How can I help to solve this ?
And last but not the least: Does mesa devs also write kernel land 
drivers or I should use the linux kernel mailing list ?

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