Add support for injecting NVSWITCH devices

This change adds support for an NVIDIA_NVSWITCH environment variable.
When set to `enabled` this striggers the injection of all available
/dev/nvidia-nvswitch* device nodes.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

CHANGELOG.md

@@ -1,5 +1,7 @@
 # NVIDIA Container Toolkit Changelog
 
+* Add support for injecting /dev/nvidia-nvswitch* devices if the NVIDIA_NVSWITCH=enabled envvar is specified.
+
 ## v1.14.6
 * Add support for extracting device major number from `/proc/devices` if `nvidia` is used as a device name over `nvidia-frontend`.
 * Add support for selecting IMEX channels using the NVIDIA_IMEX_CHANNELS environement variable.

internal/discover/nvswitch.go

@@ -0,0 +1,33 @@
+/**
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package discover
+
+import "github.com/NVIDIA/nvidia-container-toolkit/internal/logger"
+
+// NewNvSwitchDiscoverer creates a discoverer for NVSWITCH devices.
+func NewNvSwitchDiscoverer(logger logger.Interface, devRoot string) (Discover, error) {
+	devices := NewCharDeviceDiscoverer(
+		logger,
+		devRoot,
+		[]string{
+			"/dev/nvidia-nvswitchctl",
+			"/dev/nvidia-nvswitch*",
+		},
+	)
+
+	return devices, nil
+}

internal/modifier/gated.go

@@ -27,8 +27,9 @@ import (
 )
 
 const (
-	nvidiaGDSEnvvar   = "NVIDIA_GDS"
-	nvidiaMOFEDEnvvar = "NVIDIA_MOFED"
+	nvidiaGDSEnvvar      = "NVIDIA_GDS"
+	nvidiaMOFEDEnvvar    = "NVIDIA_MOFED"
+	nvidiaNVSWITCHEnvvar = "NVIDIA_NVSWITCH"
 )
 
 // NewFeatureGatedModifier creates the modifiers for optional features.
@@ -36,6 +37,7 @@ const (
 //
 //	NVIDIA_GDS=enabled
 //	NVIDIA_MOFED=enabled
+//	NVIDIA_NVSWITCH=enabled
 //
 // If not devices are selected, no changes are made.
 func NewFeatureGatedModifier(logger logger.Interface, cfg *config.Config, image image.CUDA) (oci.SpecModifier, error) {
@@ -65,5 +67,13 @@ func NewFeatureGatedModifier(logger logger.Interface, cfg *config.Config, image
 		discoverers = append(discoverers, d)
 	}
 
+	if image.Getenv(nvidiaNVSWITCHEnvvar) == "enabled" {
+		d, err := discover.NewNvSwitchDiscoverer(logger, devRoot)
+		if err != nil {
+			return nil, fmt.Errorf("failed to construct discoverer for NVSWITCH devices: %w", err)
+		}
+		discoverers = append(discoverers, d)
+	}
+
 	return NewModifierFromDiscoverer(logger, discover.Merge(discoverers...))
 }