drm/i915: evict VM instead of everything

When reserving objects during execbuf, it is possible to come across an
object which will not fit given the current fragmentation of the address
space. We do not have any defragment in drm_mm, so the strategy is to
instead evict everything, and reallocate objects.

With the upcoming addition of multiple VMs, there is no point to evict
everything since doing so is overkill for the specific case mentioned
above.

Recommended-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
[danvet: One additional s/evict_everything/evict_vm/ to update a
comment in the code.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 81ba5bb..7caf71d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2106,6 +2106,7 @@
 					  unsigned cache_level,
 					  bool mappable,
 					  bool nonblock);
+int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle);
 int i915_gem_evict_everything(struct drm_device *dev);
 
 /* i915_gem_stolen.c */