Only specify nvidia runtime if one exists

Docker may support CUDA GPUs without explicit nvidia runtime.

Signed-off-by: Emily Casey <emily.casey@docker.com>

Author: ekcasey

cmd/cli/pkg/gpu/gpu.go

@@ -19,18 +19,30 @@ const (
 
 // ProbeGPUSupport determines whether or not the Docker engine has GPU support.
 func ProbeGPUSupport(ctx context.Context, dockerClient client.SystemAPIClient) (GPUSupport, error) {
-	info, err := dockerClient.Info(ctx)
-	if err != nil {
-		return GPUSupportNone, err
-	}
-	if _, hasNvidia := info.Runtimes["nvidia"]; hasNvidia {
+	// First search for nvidia-container-runtime on PATH
+	if _, err := exec.LookPath("nvidia-container-runtime"); err == nil {
 		return GPUSupportCUDA, nil
 	}
 
-	// If nvidia runtime is not listed, try searching for nvidia-container-runtime on PATH
-	if _, err := exec.LookPath("nvidia-container-runtime"); err == nil {
+	// Next look for explicitly configured nvidia runtime. This is not required in Docker 19.03+ but
+	// may be configured on some systems
+	hasNvidia, err := HasNVIDIARuntime(ctx, dockerClient)
+	if err != nil {
+		return GPUSupportNone, err
+	}
+	if hasNvidia {
 		return GPUSupportCUDA, nil
 	}
 
 	return GPUSupportNone, nil
 }
+
+// HasNVIDIARuntime determines whether there is an nvidia runtime available
+func HasNVIDIARuntime(ctx context.Context, dockerClient client.SystemAPIClient) (bool, error) {
+	info, err := dockerClient.Info(ctx)
+	if err != nil {
+		return false, err
+	}
+	_, hasNvidia := info.Runtimes["nvidia"]
+	return hasNvidia, nil
+}

cmd/cli/pkg/standalone/containers.go

@@ -268,7 +268,9 @@ func CreateControllerContainer(ctx context.Context, dockerClient *client.Client,
 		nat.Port(portStr + "/tcp"): portBindings,
 	}
 	if gpu == gpupkg.GPUSupportCUDA {
-		hostConfig.Runtime = "nvidia"
+		if ok, err := gpupkg.HasNVIDIARuntime(ctx, dockerClient); err == nil && ok {
+			hostConfig.Runtime = "nvidia"
+		}
 		hostConfig.DeviceRequests = []container.DeviceRequest{{Count: -1, Capabilities: [][]string{{"gpu"}}}}
 	}