[PATCH] drm/amdgpu: Attach exclusive fence to prime exported bo's. (v2)

[Mario Kleiner]

External clients which import our bo's wait only
for exclusive dmabuf-fences, not on shared ones,
so attach fences on such exported buffers as
exclusive ones.

See discussion in thread:
https://lists.freedesktop.org/archives/dri-devel/2016-October/122370.html

Tested on Intel iGPU + AMD Tonga dGPU as DRI3/Present
Prime render offload, and with the Tonga standalone as
primary gpu.

v2: Add a wait for all shared fences before prime export,
    as suggested by Christian Koenig.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95472
(v1) Tested-by: Mike Lothian <mike at fireburn.co.uk>
Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Michel Dänzer <michel.daenzer at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c   | 11 +++++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 039b57e..a337d56 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -459,6 +459,7 @@ struct amdgpu_bo {
 	u64				metadata_flags;
 	void				*metadata;
 	u32				metadata_size;
+	bool				prime_exported;
 	/* list of all virtual address to which this bo
 	 * is associated to
 	 */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
index 651115d..51c6f60 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
@@ -132,7 +132,7 @@ static int amdgpu_bo_list_set(struct amdgpu_device *adev,
 		entry->priority = min(info[i].bo_priority,
 				      AMDGPU_BO_LIST_MAX_PRIORITY);
 		entry->tv.bo = &entry->robj->tbo;
-		entry->tv.shared = true;
+		entry->tv.shared = !entry->robj->prime_exported;
 
 		if (entry->robj->prefered_domains == AMDGPU_GEM_DOMAIN_GDS)
 			gds_obj = entry->robj;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
index 7700dc2..0ed92a1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
@@ -117,9 +117,20 @@ struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
 					int flags)
 {
 	struct amdgpu_bo *bo = gem_to_amdgpu_bo(gobj);
+	long ret;
 
 	if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm))
 		return ERR_PTR(-EPERM);
 
+	/*
+	 * Wait for all shared fences to complete before we switch to future
+	 * use of exclusive fence on this prime_exported bo.
+	 */
+	ret = reservation_object_wait_timeout_rcu(bo->tbo.resv, true, false,
+						  MAX_SCHEDULE_TIMEOUT);
+	WARN(ret <= 0, "Fence wait returns %li\n", ret);
+
+	bo->prime_exported = true;
+
 	return drm_gem_prime_export(dev, gobj, flags);
 }
-- 
2.7.4