drm/msm: Add _NO_SHARE flag

Buffers that are not shared between contexts can share a single resv
object.  This way drm_gpuvm will not track them as external objects, and
submit-time validating overhead will be O(1) for all N non-shared BOs,
instead of O(n).

Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Tested-by: Antonino Maniscalco <antomani103@gmail.com>
Reviewed-by: Antonino Maniscalco <antomani103@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/661497/

include/uapi/drm/msm_drm.h

@@ -140,6 +140,19 @@ struct drm_msm_param {
 
 #define MSM_BO_SCANOUT       0x00000001     /* scanout capable */
 #define MSM_BO_GPU_READONLY  0x00000002
+/* Private buffers do not need to be explicitly listed in the SUBMIT
+ * ioctl, unless referenced by a drm_msm_gem_submit_cmd.  Private
+ * buffers may NOT be imported/exported or used for scanout (or any
+ * other situation where buffers can be indefinitely pinned, but
+ * cases other than scanout are all kernel owned BOs which are not
+ * visible to userspace).
+ *
+ * In exchange for those constraints, all private BOs associated with
+ * a single context (drm_file) share a single dma_resv, and if there
+ * has been no eviction since the last submit, there are no per-BO
+ * bookeeping to do, significantly cutting the SUBMIT overhead.
+ */
+#define MSM_BO_NO_SHARE      0x00000004
 #define MSM_BO_CACHE_MASK    0x000f0000
 /* cache modes */
 #define MSM_BO_CACHED        0x00010000
@@ -149,6 +162,7 @@ struct drm_msm_param {
 
 #define MSM_BO_FLAGS         (MSM_BO_SCANOUT | \
                               MSM_BO_GPU_READONLY | \
+                              MSM_BO_NO_SHARE | \
                               MSM_BO_CACHE_MASK)
 
 struct drm_msm_gem_new {