[nvpassthrough] do not load kernel modules unless user opts-in

Signed-off-by: Christopher Desiniotis <cdesiniotis@nvidia.com>

Author: cdesiniotis

pkg/nvpassthrough/nvpassthrough.go

@@ -44,9 +44,10 @@ type Interface interface {
 }
 
 type nvpassthrough struct {
-	logger         basicLogger
-	libModulesRoot string
-	nvpciLib       nvpci.Interface
+	logger            basicLogger
+	libModulesRoot    string
+	nvpciLib          nvpci.Interface
+	loadKernelModules bool
 }
 
 var _ Interface = (*nvpassthrough)(nil)
@@ -92,6 +93,15 @@ func WithLibModulesRoot(libModulesRoot string) Option {
 	}
 }
 
+// WithLoadKernelModules provides an Option for opting-in to loading
+// kernel modules before binding NVIDIA PCI devices to them. By default,
+// this behavior is disabled.
+func WithLoadKernelModules(loadKernelModules bool) Option {
+	return func(w *nvpassthrough) {
+		w.loadKernelModules = loadKernelModules
+	}
+}
+
 // WithNvpciLib provides an Option to set the nvpci lib used.
 func WithNvpciLib(lib nvpci.Interface) Option {
 	return func(w *nvpassthrough) {
@@ -168,15 +178,10 @@ func (n *nvpassthrough) BindToVFIODriver(address string) error {
 		return fmt.Errorf("failed to find best vfio variant driver: %w", err)
 	}
 
-	k, err := kmod.New(
-		kmod.SetInitFunc(modInitFunc),
-		kmod.SetRootDir(n.libModulesRoot),
-	)
-	if err != nil {
-		return fmt.Errorf("failed to initialize kmod library: %w", err)
-	}
-	if err := k.Load(vfioDriverName, "", 0); err != nil {
-		return fmt.Errorf("failed to load %q driver: %w", vfioDriverName, err)
+	if n.loadKernelModules {
+		if err := n.loadKernelModule(vfioDriverName); err != nil {
+			return fmt.Errorf("failed to load %q driver: %w", vfioDriverName, err)
+		}
 	}
 
 	// (cdesiniotis) Module names in the modules.alias file will only ever contain
@@ -239,6 +244,21 @@ func (n *nvpassthrough) BindToVFIODriver(address string) error {
 	return nil
 }
 
+func (n *nvpassthrough) loadKernelModule(moduleName string) error {
+	k, err := kmod.New(
+		kmod.SetInitFunc(modInitFunc),
+		kmod.SetRootDir(n.libModulesRoot),
+	)
+	if err != nil {
+		return fmt.Errorf("failed to initialize kmod library: %w", err)
+	}
+	if err := k.Load(moduleName, "", 0); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // BindToDriver binds an NVIDIA PCI device to the driver supplied as input.
 func (n *nvpassthrough) BindToDriver(address string, driver string) error {
 	device, err := n.nvpciLib.GetNvidiaDeviceByPciBusID(address)