docs: Sample driver to demonstrate how to use Mediated device framework.

other IOMMU backend modules, such as PPC64 sPAPR module, they need to provide

other IOMMU backend modules, such as PPC64 sPAPR module, they need to provide

these two callback functions.

these two callback functions.

Using the Sample Code

=====================

mtty.c in samples/vfio-mdev/ directory is a sample driver program to

demonstrate how to use the mediated device framework.

The sample driver creates an mdev device that simulates a serial port over a PCI

card.

1. Build and load the mtty.ko module.

   This step creates a dummy device, /sys/devices/virtual/mtty/mtty/

   Files in this device directory in sysfs are similar to the following:

   # tree /sys/devices/virtual/mtty/mtty/

      /sys/devices/virtual/mtty/mtty/

      |-- mdev_supported_types

      |   |-- mtty-1

      |   |   |-- available_instances

      |   |   |-- create

      |   |   |-- device_api

      |   |   |-- devices

      |   |   `-- name

      |   `-- mtty-2

      |       |-- available_instances

      |       |-- create

      |       |-- device_api

      |       |-- devices

      |       `-- name

      |-- mtty_dev

      |   `-- sample_mtty_dev

      |-- power

      |   |-- autosuspend_delay_ms

      |   |-- control

      |   |-- runtime_active_time

      |   |-- runtime_status

      |   `-- runtime_suspended_time

      |-- subsystem -> ../../../../class/mtty

      `-- uevent

2. Create a mediated device by using the dummy device that you created in the

   previous step.

   # echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" >	\

              /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create

3. Add parameters to qemu-kvm.

   -device vfio-pci,\

    sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001

4. Boot the VM.

   In the Linux guest VM, with no hardware on the host, the device appears

   as  follows:

   # lspci -s 00:05.0 -xxvv

   00:05.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550])

           Subsystem: Device 4348:3253

           Physical Slot: 5

           Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-

   Stepping- SERR- FastB2B- DisINTx-

           Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort-

   <TAbort- <MAbort- >SERR- <PERR- INTx-

           Interrupt: pin A routed to IRQ 10

           Region 0: I/O ports at c150 [size=8]

           Region 1: I/O ports at c158 [size=8]

           Kernel driver in use: serial

   00: 48 43 53 32 01 00 00 02 10 02 00 07 00 00 00 00

   10: 51 c1 00 00 59 c1 00 00 00 00 00 00 00 00 00 00

   20: 00 00 00 00 00 00 00 00 00 00 00 00 48 43 53 32

   30: 00 00 00 00 00 00 00 00 00 00 00 00 0a 01 00 00

   In the Linux guest VM, dmesg output for the device is as follows:

   serial 0000:00:05.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, high) -> IRQ

10

   0000:00:05.0: ttyS1 at I/O 0xc150 (irq = 10) is a 16550A

   0000:00:05.0: ttyS2 at I/O 0xc158 (irq = 10) is a 16550A

5. In the Linux guest VM, check the serial ports.

   # setserial -g /dev/ttyS*

   /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4

   /dev/ttyS1, UART: 16550A, Port: 0xc150, IRQ: 10

   /dev/ttyS2, UART: 16550A, Port: 0xc158, IRQ: 10

6. Using a minicom or any terminal enulation program, open port /dev/ttyS1 or

   /dev/ttyS2 with hardware flow control disabled.

7. Type data on the minicom terminal or send data to the terminal emulation

   program and read the data.

   Data is loop backed from hosts mtty driver.

8. Destroy the mediated device that you created.

   # echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001/remove

References

References

----------

==========

[1] See Documentation/vfio.txt for more information on VFIO.

[1] See Documentation/vfio.txt for more information on VFIO.

[2] struct mdev_driver in include/linux/mdev.h

[2] struct mdev_driver in include/linux/mdev.h

#

# Makefile for mtty.c file

#

KERNEL_DIR:=/lib/modules/$(shell uname -r)/build

obj-m:=mtty.o

modules clean modules_install:

	$(MAKE) -C $(KERNEL_DIR) SUBDIRS=$(PWD) $@

default: modules

module: modules