virtcontainers: handle persistent memory volumes

A persistent memory volume MUST meet the following conditions:
* A loop device must be mounted in the directory passed as volume
* The loop device must have a backing file
* The backing file must have the PFN signature at offset 4k [1][2]

The backing file is used as backend file for a NVDIMM device in the guest

fixes kata-containers#2262

[1] - https://github.com/kata-containers/osbuilder/blob/master/image-builder
/nsdax.gpl.c
[2] - https://github.com/torvalds/linux/blob/master/drivers/nvdimm/pfn.h

Signed-off-by: Julio Montes <julio.montes@intel.com>

virtcontainers/kata_agent.go

@@ -1101,6 +1101,13 @@ func (k *kataAgent) appendDevices(deviceList []*grpc.Device, c *Container) []*gr
 			continue
 		}
 
+		if d.Pmem {
+			// block drive is a persistent memory device that
+			// was passed as volume (-v) not as device (--device).
+			// It shouldn't be visible in the container
+			continue
+		}
+
 		kataDevice := &grpc.Device{
 			ContainerPath: dev.ContainerPath,
 		}
@@ -1439,7 +1446,18 @@ func (k *kataAgent) handleBlockVolumes(c *Container) ([]*grpc.Storage, error) {
 			k.Logger().Error("malformed block drive")
 			continue
 		}
+
+		vol.MountPoint = m.Destination
+		vol.Fstype = "bind"
+		vol.Options = []string{"bind"}
+
 		switch {
+		// pmem volumes case
+		case blockDrive.Pmem:
+			vol.Driver = kataNvdimmDevType
+			vol.Source = fmt.Sprintf("/dev/pmem%s", blockDrive.NvdimmID)
+			vol.Fstype = blockDrive.Format
+			vol.Options = []string{"dax"}
 		case c.sandbox.config.HypervisorConfig.BlockDeviceDriver == config.VirtioBlockCCW:
 			vol.Driver = kataBlkCCWDevType
 			vol.Source = blockDrive.DevNo
@@ -1456,10 +1474,6 @@ func (k *kataAgent) handleBlockVolumes(c *Container) ([]*grpc.Storage, error) {
 			return nil, fmt.Errorf("Unknown block device driver: %s", c.sandbox.config.HypervisorConfig.BlockDeviceDriver)
 		}
 
-		vol.MountPoint = m.Destination
-		vol.Fstype = "bind"
-		vol.Options = []string{"bind"}
-
 		volumeStorages = append(volumeStorages, vol)
 	}