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authorMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-06-27 15:39:22 -0300
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-07-15 11:03:02 -0300
commitbaa293e9544bea71361950d071579f0e4d5713ed (patch)
tree29e0400c806016783a3fd7a380be40a201956653 /Documentation/vfio-mediated-device.txt
parent4f4cfa6c560c93ba180c30675cf845e1597de44c (diff)
docs: driver-api: add a series of orphaned documents
There are lots of documents under Documentation/*.txt and a few other orphan documents elsehwere that belong to the driver-API book. Move them to their right place. Reviewed-by: Cornelia Huck <cohuck@redhat.com> # vfio-related parts Acked-by: Logan Gunthorpe <logang@deltatee.com> # switchtec Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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-.. include:: <isonum.txt>
-
-=====================
-VFIO Mediated devices
-=====================
-
-:Copyright: |copy| 2016, NVIDIA CORPORATION. All rights reserved.
-:Author: Neo Jia <cjia@nvidia.com>
-:Author: Kirti Wankhede <kwankhede@nvidia.com>
-
-This program is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License version 2 as
-published by the Free Software Foundation.
-
-
-Virtual Function I/O (VFIO) Mediated devices[1]
-===============================================
-
-The number of use cases for virtualizing DMA devices that do not have built-in
-SR_IOV capability is increasing. Previously, to virtualize such devices,
-developers had to create their own management interfaces and APIs, and then
-integrate them with user space software. To simplify integration with user space
-software, we have identified common requirements and a unified management
-interface for such devices.
-
-The VFIO driver framework provides unified APIs for direct device access. It is
-an IOMMU/device-agnostic framework for exposing direct device access to user
-space in a secure, IOMMU-protected environment. This framework is used for
-multiple devices, such as GPUs, network adapters, and compute accelerators. With
-direct device access, virtual machines or user space applications have direct
-access to the physical device. This framework is reused for mediated devices.
-
-The mediated core driver provides a common interface for mediated device
-management that can be used by drivers of different devices. This module
-provides a generic interface to perform these operations:
-
-* Create and destroy a mediated device
-* Add a mediated device to and remove it from a mediated bus driver
-* Add a mediated device to and remove it from an IOMMU group
-
-The mediated core driver also provides an interface to register a bus driver.
-For example, the mediated VFIO mdev driver is designed for mediated devices and
-supports VFIO APIs. The mediated bus driver adds a mediated device to and
-removes it from a VFIO group.
-
-The following high-level block diagram shows the main components and interfaces
-in the VFIO mediated driver framework. The diagram shows NVIDIA, Intel, and IBM
-devices as examples, as these devices are the first devices to use this module::
-
- +---------------+
- | |
- | +-----------+ | mdev_register_driver() +--------------+
- | | | +<------------------------+ |
- | | mdev | | | |
- | | bus | +------------------------>+ vfio_mdev.ko |<-> VFIO user
- | | driver | | probe()/remove() | | APIs
- | | | | +--------------+
- | +-----------+ |
- | |
- | MDEV CORE |
- | MODULE |
- | mdev.ko |
- | +-----------+ | mdev_register_device() +--------------+
- | | | +<------------------------+ |
- | | | | | nvidia.ko |<-> physical
- | | | +------------------------>+ | device
- | | | | callbacks +--------------+
- | | Physical | |
- | | device | | mdev_register_device() +--------------+
- | | interface | |<------------------------+ |
- | | | | | i915.ko |<-> physical
- | | | +------------------------>+ | device
- | | | | callbacks +--------------+
- | | | |
- | | | | mdev_register_device() +--------------+
- | | | +<------------------------+ |
- | | | | | ccw_device.ko|<-> physical
- | | | +------------------------>+ | device
- | | | | callbacks +--------------+
- | +-----------+ |
- +---------------+
-
-
-Registration Interfaces
-=======================
-
-The mediated core driver provides the following types of registration
-interfaces:
-
-* Registration interface for a mediated bus driver
-* Physical device driver interface
-
-Registration Interface for a Mediated Bus Driver
-------------------------------------------------
-
-The registration interface for a mediated bus driver provides the following
-structure to represent a mediated device's driver::
-
- /*
- * struct mdev_driver [2] - Mediated device's driver
- * @name: driver name
- * @probe: called when new device created
- * @remove: called when device removed
- * @driver: device driver structure
- */
- struct mdev_driver {
- const char *name;
- int (*probe) (struct device *dev);
- void (*remove) (struct device *dev);
- struct device_driver driver;
- };
-
-A mediated bus driver for mdev should use this structure in the function calls
-to register and unregister itself with the core driver:
-
-* Register::
-
- extern int mdev_register_driver(struct mdev_driver *drv,
- struct module *owner);
-
-* Unregister::
-
- extern void mdev_unregister_driver(struct mdev_driver *drv);
-
-The mediated bus driver is responsible for adding mediated devices to the VFIO
-group when devices are bound to the driver and removing mediated devices from
-the VFIO when devices are unbound from the driver.
-
-
-Physical Device Driver Interface
---------------------------------
-
-The physical device driver interface provides the mdev_parent_ops[3] structure
-to define the APIs to manage work in the mediated core driver that is related
-to the physical device.
-
-The structures in the mdev_parent_ops structure are as follows:
-
-* dev_attr_groups: attributes of the parent device
-* mdev_attr_groups: attributes of the mediated device
-* supported_config: attributes to define supported configurations
-
-The functions in the mdev_parent_ops structure are as follows:
-
-* create: allocate basic resources in a driver for a mediated device
-* remove: free resources in a driver when a mediated device is destroyed
-
-(Note that mdev-core provides no implicit serialization of create/remove
-callbacks per mdev parent device, per mdev type, or any other categorization.
-Vendor drivers are expected to be fully asynchronous in this respect or
-provide their own internal resource protection.)
-
-The callbacks in the mdev_parent_ops structure are as follows:
-
-* open: open callback of mediated device
-* close: close callback of mediated device
-* ioctl: ioctl callback of mediated device
-* read : read emulation callback
-* write: write emulation callback
-* mmap: mmap emulation callback
-
-A driver should use the mdev_parent_ops structure in the function call to
-register itself with the mdev core driver::
-
- extern int mdev_register_device(struct device *dev,
- const struct mdev_parent_ops *ops);
-
-However, the mdev_parent_ops structure is not required in the function call
-that a driver should use to unregister itself with the mdev core driver::
-
- extern void mdev_unregister_device(struct device *dev);
-
-
-Mediated Device Management Interface Through sysfs
-==================================================
-
-The management interface through sysfs enables user space software, such as
-libvirt, to query and configure mediated devices in a hardware-agnostic fashion.
-This management interface provides flexibility to the underlying physical
-device's driver to support features such as:
-
-* Mediated device hot plug
-* Multiple mediated devices in a single virtual machine
-* Multiple mediated devices from different physical devices
-
-Links in the mdev_bus Class Directory
--------------------------------------
-The /sys/class/mdev_bus/ directory contains links to devices that are registered
-with the mdev core driver.
-
-Directories and files under the sysfs for Each Physical Device
---------------------------------------------------------------
-
-::
-
- |- [parent physical device]
- |--- Vendor-specific-attributes [optional]
- |--- [mdev_supported_types]
- | |--- [<type-id>]
- | | |--- create
- | | |--- name
- | | |--- available_instances
- | | |--- device_api
- | | |--- description
- | | |--- [devices]
- | |--- [<type-id>]
- | | |--- create
- | | |--- name
- | | |--- available_instances
- | | |--- device_api
- | | |--- description
- | | |--- [devices]
- | |--- [<type-id>]
- | |--- create
- | |--- name
- | |--- available_instances
- | |--- device_api
- | |--- description
- | |--- [devices]
-
-* [mdev_supported_types]
-
- The list of currently supported mediated device types and their details.
-
- [<type-id>], device_api, and available_instances are mandatory attributes
- that should be provided by vendor driver.
-
-* [<type-id>]
-
- The [<type-id>] name is created by adding the device driver string as a prefix
- to the string provided by the vendor driver. This format of this name is as
- follows::
-
- sprintf(buf, "%s-%s", dev_driver_string(parent->dev), group->name);
-
- (or using mdev_parent_dev(mdev) to arrive at the parent device outside
- of the core mdev code)
-
-* device_api
-
- This attribute should show which device API is being created, for example,
- "vfio-pci" for a PCI device.
-
-* available_instances
-
- This attribute should show the number of devices of type <type-id> that can be
- created.
-
-* [device]
-
- This directory contains links to the devices of type <type-id> that have been
- created.
-
-* name
-
- This attribute should show human readable name. This is optional attribute.
-
-* description
-
- This attribute should show brief features/description of the type. This is
- optional attribute.
-
-Directories and Files Under the sysfs for Each mdev Device
-----------------------------------------------------------
-
-::
-
- |- [parent phy device]
- |--- [$MDEV_UUID]
- |--- remove
- |--- mdev_type {link to its type}
- |--- vendor-specific-attributes [optional]
-
-* remove (write only)
-
-Writing '1' to the 'remove' file destroys the mdev device. The vendor driver can
-fail the remove() callback if that device is active and the vendor driver
-doesn't support hot unplug.
-
-Example::
-
- # echo 1 > /sys/bus/mdev/devices/$mdev_UUID/remove
-
-Mediated device Hot plug
-------------------------
-
-Mediated devices can be created and assigned at runtime. The procedure to hot
-plug a mediated device is the same as the procedure to hot plug a PCI device.
-
-Translation APIs for Mediated Devices
-=====================================
-
-The following APIs are provided for translating user pfn to host pfn in a VFIO
-driver::
-
- extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
- int npage, int prot, unsigned long *phys_pfn);
-
- extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
- int npage);
-
-These functions call back into the back-end IOMMU module by using the pin_pages
-and unpin_pages callbacks of the struct vfio_iommu_driver_ops[4]. Currently
-these callbacks are supported in the TYPE1 IOMMU module. To enable them for
-other IOMMU backend modules, such as PPC64 sPAPR module, they need to provide
-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 minicom or any terminal emulation 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
-==========
-
-1. See Documentation/vfio.txt for more information on VFIO.
-2. struct mdev_driver in include/linux/mdev.h
-3. struct mdev_parent_ops in include/linux/mdev.h
-4. struct vfio_iommu_driver_ops in include/linux/vfio.h