(In reply to smoki from comment #32)
>  As of mesa commit 7b4276d7acf2e0f77044cb50caa6ad936fa78786 -mtune=generic
> works normal. 
> 

 After further testing actually this fixed major fps drops with -mtune=generic,
but there is still very worse stuter in (m)any games with it , so i not
considered still this as fixed.

 I also tried this patch https://bugs.freedesktop.org/attachment.cgi?id=107655 
to remove corruption after that commit, it helps for that... but -mtune=generic
is not fixed, i need to patch mesa too to remove any occuranes of GTT_WC then
-mtune=generic works fine for me.