qat: do not fail if driver/unbind file does not exist

<device>/driver symlink does not exist if the device is not bound
to any driver. bindDevice() failed when writing to <device>/driver/unbind
errored but IsNotExist() error is acceptable in case there's no driver
to unbind.

Signed-off-by: Mikko Ylinen <mikko.ylinen@intel.com>

Author: mythi

cmd/qat_plugin/dpdkdrv/dpdkdrv.go

@@ -1,4 +1,4 @@
-// Copyright 2017 Intel Corporation. All Rights Reserved.
+// Copyright 2017-2021 Intel 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.
@@ -201,9 +201,8 @@ func (dp *DevicePlugin) getDeviceID(pciAddr string) (string, error) {
 func (dp *DevicePlugin) bindDevice(vfBdf string) error {
 	unbindDevicePath := filepath.Join(dp.pciDeviceDir, vfBdf, driverUnbindSuffix)
 
-	// Unbind from the kernel driver
-	err := os.WriteFile(unbindDevicePath, []byte(vfBdf), 0600)
-	if err != nil {
+	// Unbind from the kernel driver. IsNotExist means the device is not bound to any driver.
+	if err := os.WriteFile(unbindDevicePath, []byte(vfBdf), 0600); !os.IsNotExist(err) {
 		return errors.Wrapf(err, "Unbinding from kernel driver failed for the device %s", vfBdf)
 	}
 	vfdevID, err := dp.getDeviceID(vfBdf)
@@ -319,7 +318,7 @@ func getCurrentDriver(device string) string {
 	symlink := filepath.Join(device, "driver")
 	driver, err := filepath.EvalSymlinks(symlink)
 	if err != nil {
-		klog.Warningf("unable to evaluate symlink: %s", symlink)
+		klog.Infof("no driver bound to device %q", filepath.Base(device))
 		return ""
 	}
 	return filepath.Base(driver)

cmd/qat_plugin/dpdkdrv/dpdkdrv_test.go

@@ -295,6 +295,28 @@ func TestScanPrivate(t *testing.T) {
 			maxDevNum:      1,
 			expectedDevNum: 1,
 		},
+		{
+			name:            "vfio-pci DPDKdriver with no kernel bound driver and where vfdevID is equal to qatDevId (37c9)",
+			dpdkDriver:      "vfio-pci",
+			kernelVfDrivers: []string{"c6xxvf"},
+			dirs: []string{
+				"sys/bus/pci/drivers/c6xx",
+				"sys/bus/pci/drivers/vfio-pci",
+				"sys/bus/pci/devices/0000:02:00.0",
+				"sys/bus/pci/devices/0000:02:01.0",
+			},
+			files: map[string][]byte{
+				"sys/bus/pci/devices/0000:02:01.0/device": []byte("0x37c9"),
+				"sys/bus/pci/drivers/vfio-pci/new_id":     []byte("some junk"),
+			},
+			symlinks: map[string]string{
+				"sys/bus/pci/devices/0000:02:01.0/iommu_group": "sys/kernel/iommu_groups/vfiotestfile",
+				"sys/bus/pci/drivers/c6xx/0000:02:00.0":        "sys/bus/pci/devices/0000:02:00.0",
+				"sys/bus/pci/devices/0000:02:00.0/virtfn0":     "sys/bus/pci/devices/0000:02:01.0",
+			},
+			maxDevNum:      1,
+			expectedDevNum: 1,
+		},
 		{
 			name:            "vfio-pci DPDKdriver with one kernel bound device (QAT device) where vfdevID is equal to qatDevId not enabbled in kernelVfDrivers",
 			dpdkDriver:      "vfio-pci",