Refactor how mdev's are represented internally in nvmdev.

The 'mdev' string now represents the absolute path to an
mdev device (/sys/bus/pci/devices/<addr>/<uuid>) instead
of the  mdev_type directory for the mdev device
(/sys/bus/pci/devices/<addr>/mdev_supported_types/<mdev-type>).
This is more intuitive and will make it easier to get
more information about a particular mdev device -
like the driver or iommu_group it belongs to - which can
be found at /sys/bus/pci/devices/<addr>/<uuid>.

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

pkg/nvmdev/mock.go

@@ -183,14 +183,20 @@ func (m *MockNvmdev) AddMockA100Parent(address string, numaNode int) error {
 
 // AddMockA100Mdev creates an A100 like MDEV (vGPU) mock device.
 // The corresponding mocked parent A100 device must be created beforehand.
-func (m *MockNvmdev) AddMockA100Mdev(uuid string, mdevType string, parentMdevTypeDir string) error {
+func (m *MockNvmdev) AddMockA100Mdev(uuid string, mdevType string, mdevTypeDir string, parentDeviceDir string) error {
-	deviceDir := filepath.Join(m.mdevDevicesRoot, uuid)
+	mdevDeviceDir := filepath.Join(parentDeviceDir, uuid)
-	err := os.MkdirAll(deviceDir, 0755)
+	err := os.Mkdir(mdevDeviceDir, 0755)
 	if err != nil {
 		return err
 	}
 
-	err = os.Symlink(parentMdevTypeDir, filepath.Join(deviceDir, "mdev_type"))
+	parentMdevTypeDir := filepath.Join(parentDeviceDir, "mdev_supported_types", mdevTypeDir)
+	err = os.Symlink(parentMdevTypeDir, filepath.Join(mdevDeviceDir, "mdev_type"))
+	if err != nil {
+		return err
+	}
+
+	err = os.Symlink(mdevDeviceDir, filepath.Join(m.mdevDevicesRoot, uuid))
 	if err != nil {
 		return err
 	}

pkg/nvmdev/nvmdev.go

@@ -153,27 +153,33 @@ func NewDevice(root string, uuid string) (*Device, error) {
 	return &device, nil
 }
 
+// mdev represents the path to an NVIDIA mdev (vGPU) device.
 type mdev string
 
 func newMdev(devicePath string) (mdev, error) {
-	mdevTypeDir, err := filepath.EvalSymlinks(path.Join(devicePath, "mdev_type"))
+	mdevDir, err := filepath.EvalSymlinks(devicePath)
 	if err != nil {
-		return "", fmt.Errorf("error resolving mdev_type link: %v", err)
+		return "", fmt.Errorf("error resolving symlink for %s: %v", devicePath, err)
 	}
 
-	return mdev(mdevTypeDir), nil
+	return mdev(mdevDir), nil
 }
 
 func (m mdev) String() string {
 	return string(m)
 }
 func (m mdev) parentDevicePath() string {
-	// /sys/bus/pci/devices/<addr>/mdev_supported_types/<mdev_type>
+	// /sys/bus/pci/devices/<addr>/<uuid>
-	return path.Dir(path.Dir(string(m)))
+	return path.Dir(string(m))
 }
 
 func (m mdev) Type() (string, error) {
-	mdevType, err := os.ReadFile(path.Join(string(m), "name"))
+	mdevTypeDir, err := filepath.EvalSymlinks(path.Join(string(m), "mdev_type"))
+	if err != nil {
+		return "", fmt.Errorf("error resolving mdev_type link for mdev %s: %v", m, err)
+	}
+
+	mdevType, err := os.ReadFile(path.Join(mdevTypeDir, "name"))
 	if err != nil {
 		return "", fmt.Errorf("unable to read mdev_type name for mdev %s: %v", m, err)
 	}

pkg/nvmdev/nvmdev_test.go

@@ -18,7 +18,6 @@ package nvmdev
 
 import (
 	"github.com/stretchr/testify/require"
-	"path/filepath"
 	"testing"
 )
 
@@ -41,8 +40,7 @@ func TestNvmdev(t *testing.T) {
 	require.Nil(t, err, "Error checking if A100-4Q vGPU type is available for creation")
 	require.True(t, available, "A100-4C should be available to create")
 
-	err = nvmdev.AddMockA100Mdev("b1914f0a-15cf-416e-8967-55fc7cb68e20", "A100-4C",
+	err = nvmdev.AddMockA100Mdev("b1914f0a-15cf-416e-8967-55fc7cb68e20", "A100-4C", "nvidia-500", parentDevs[0].Path)
-		filepath.Join(parentDevs[0].Path, "mdev_supported_types/nvidia-500"))
 	require.Nil(t, err, "Error adding Mock A100 mediated device")
 
 	mdevs, err := nvmdev.GetAllDevices()