drm/amdgpu:fix world switch hang

for SR-IOV, we must keep the pipeline-sync in the protection
of COND_EXEC, otherwise the command consumed by CPG is not
consistent when world switch triggerd, e.g.:

world switch hit and the IB frame is skipped so the fence
won't signal, thus CP will jump to the next DMAframe's pipeline-sync
command, and it will make CP hang foever.

after pipelin-sync moved into COND_EXEC the consistency can be
guaranteed

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c

@@ -130,6 +130,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 
 	unsigned i;
 	int r = 0;
+	bool need_pipe_sync = false;
 
 	if (num_ibs == 0)
 		return -EINVAL;
@@ -165,7 +166,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 	if (ring->funcs->emit_pipeline_sync && job &&
 	    ((tmp = amdgpu_sync_get_fence(&job->sched_sync)) ||
 	     amdgpu_vm_need_pipeline_sync(ring, job))) {
-		amdgpu_ring_emit_pipeline_sync(ring);
+		need_pipe_sync = true;
 		dma_fence_put(tmp);
 	}
 
@@ -173,7 +174,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 		ring->funcs->insert_start(ring);
 
 	if (job) {
-		r = amdgpu_vm_flush(ring, job);
+		r = amdgpu_vm_flush(ring, job, need_pipe_sync);
 		if (r) {
 			amdgpu_ring_undo(ring);
 			return r;

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -743,7 +743,7 @@ static bool amdgpu_vm_is_large_bar(struct amdgpu_device *adev)
  *
  * Emit a VM flush when it is necessary.
  */
-int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job)
+int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_pipe_sync)
 {
 	struct amdgpu_device *adev = ring->adev;
 	unsigned vmhub = ring->funcs->vmhub;
@@ -765,12 +765,15 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job)
 		vm_flush_needed = true;
 	}
 
-	if (!vm_flush_needed && !gds_switch_needed)
+	if (!vm_flush_needed && !gds_switch_needed && !need_pipe_sync)
 		return 0;
 
 	if (ring->funcs->init_cond_exec)
 		patch_offset = amdgpu_ring_init_cond_exec(ring);
 
+	if (need_pipe_sync)
+		amdgpu_ring_emit_pipeline_sync(ring);
+
 	if (ring->funcs->emit_vm_flush && vm_flush_needed) {
 		struct dma_fence *fence;
 

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h

@@ -222,7 +222,7 @@ int amdgpu_vm_alloc_pts(struct amdgpu_device *adev,
 int amdgpu_vm_grab_id(struct amdgpu_vm *vm, struct amdgpu_ring *ring,
 		      struct amdgpu_sync *sync, struct dma_fence *fence,
 		      struct amdgpu_job *job);
-int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job);
+int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_pipe_sync);
 void amdgpu_vm_reset_id(struct amdgpu_device *adev, unsigned vmhub,
 			unsigned vmid);
 void amdgpu_vm_reset_all_ids(struct amdgpu_device *adev);