drm/amdgpu: grab the id mgr lock while accessing passid_mapping

Need to make sure that we actually dropping the right fence.
Could be done with RCU as well, but to complicated for a fix.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1036,10 +1036,8 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_
 		id->oa_base != job->oa_base ||
 		id->oa_size != job->oa_size);
 	bool vm_flush_needed = job->vm_needs_flush;
-	bool pasid_mapping_needed = id->pasid != job->pasid ||
-		!id->pasid_mapping ||
-		!dma_fence_is_signaled(id->pasid_mapping);
 	struct dma_fence *fence = NULL;
+	bool pasid_mapping_needed;
 	unsigned patch_offset = 0;
 	int r;
 
@@ -1049,6 +1047,12 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_
 		pasid_mapping_needed = true;
 	}
 
+	mutex_lock(&id_mgr->lock);
+	if (id->pasid != job->pasid || !id->pasid_mapping ||
+	    !dma_fence_is_signaled(id->pasid_mapping))
+		pasid_mapping_needed = true;
+	mutex_unlock(&id_mgr->lock);
+
 	gds_switch_needed &= !!ring->funcs->emit_gds_switch;
 	vm_flush_needed &= !!ring->funcs->emit_vm_flush  &&
 			job->vm_pd_addr != AMDGPU_BO_INVALID_OFFSET;
@@ -1088,9 +1092,11 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_
 	}
 
 	if (pasid_mapping_needed) {
+		mutex_lock(&id_mgr->lock);
 		id->pasid = job->pasid;
 		dma_fence_put(id->pasid_mapping);
 		id->pasid_mapping = dma_fence_get(fence);
+		mutex_unlock(&id_mgr->lock);
 	}
 	dma_fence_put(fence);