drm/i915: Only skip updating execobject.offset after error

I was being overly paranoid in not updating the execobject.offset after
performing the fallback copy where we set reloc.presumed_offset to -1.
The thinking was to ensure that a subsequent NORELOC execbuf would be
forced to process the invalid relocations. However this is overkill so
long as we *only* update the execobject.offset following a successful
update of the relocation value witin the batch. If we have to repeat the
execbuf due to a later interruption, then we may skip the relocations on
the second pass (honouring NORELOC) since the execobject.offset match
the actual offsets (even though reloc.presumed_offset is garbage).

Subsequent calls to execbuf with NORELOC should themselves ensure that
the reloc.presumed_offset have been corrected in case of future
migration.

Reporting back the actual execobject.offset, even when
reloc.presumed_offset is garbage, ensures that reuse of those objects
use the latest information to avoid relocations.

Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101635
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170721145037.25105-4-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index f30675c..ae47e18 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1776,7 +1776,7 @@ out:
                }
        }
 
-       return err ?: have_copy;
+       return err;
 }
 
 static int eb_relocate(struct i915_execbuffer *eb)
@@ -2210,7 +2210,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
                goto err_rpm;
 
        err = eb_relocate(&eb);
-       if (err)
+       if (err) {
                /*
                 * If the user expects the execobject.offset and
                 * reloc.presumed_offset to be an exact match,
@@ -2219,8 +2219,8 @@ i915_gem_do_execbuffer(struct drm_device *dev,
                 * relocation.
                 */
                args->flags &= ~__EXEC_HAS_RELOC;
-       if (err < 0)
                goto err_vma;
+       }
 
        if (unlikely(eb.batch->exec_entry->flags & EXEC_OBJECT_WRITE)) {
                DRM_DEBUG("Attempting to use self-modifying batch buffer\n");