mirror of
https://github.com/torvalds/linux.git
synced 2024-12-08 20:21:34 +00:00
3232868133
The nvidia mdev driver does not actually exist anywhere in the tree. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com> Link: https://lore.kernel.org/r/20230110091009.474427-5-hch@lst.de Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
274 lines
9.5 KiB
ReStructuredText
274 lines
9.5 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0-only
|
|
.. 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>
|
|
|
|
|
|
|
|
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_parent() +--------------+
|
|
| | | +<------------------------+ |
|
|
| | | | | ccw_device.ko|<-> physical
|
|
| | | +------------------------>+ | device
|
|
| | | | callbacks +--------------+
|
|
| | Physical | |
|
|
| | device | | mdev_register_parent() +--------------+
|
|
| | interface | |<------------------------+ |
|
|
| | | | | i915.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 device driver provides the following
|
|
structure to represent a mediated device's driver::
|
|
|
|
/*
|
|
* struct mdev_driver [2] - Mediated device's driver
|
|
* @probe: called when new device created
|
|
* @remove: called when device removed
|
|
* @driver: device driver structure
|
|
*/
|
|
struct mdev_driver {
|
|
int (*probe) (struct mdev_device *dev);
|
|
void (*remove) (struct mdev_device *dev);
|
|
unsigned int (*get_available)(struct mdev_type *mtype);
|
|
ssize_t (*show_description)(struct mdev_type *mtype, char *buf);
|
|
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::
|
|
|
|
int mdev_register_driver(struct mdev_driver *drv);
|
|
|
|
* Unregister::
|
|
|
|
void mdev_unregister_driver(struct mdev_driver *drv);
|
|
|
|
The mediated bus driver's probe function should create a vfio_device on top of
|
|
the mdev_device and connect it to an appropriate implementation of
|
|
vfio_device_ops.
|
|
|
|
When a driver wants to add the GUID creation sysfs to an existing device it has
|
|
probe'd to then it should call::
|
|
|
|
int mdev_register_parent(struct mdev_parent *parent, struct device *dev,
|
|
struct mdev_driver *mdev_driver);
|
|
|
|
This will provide the 'mdev_supported_types/XX/create' files which can then be
|
|
used to trigger the creation of a mdev_device. The created mdev_device will be
|
|
attached to the specified driver.
|
|
|
|
When the driver needs to remove itself it calls::
|
|
|
|
void mdev_unregister_parent(struct mdev_parent *parent);
|
|
|
|
Which will unbind and destroy all the created mdevs and remove the sysfs files.
|
|
|
|
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);
|
|
|
|
* device_api
|
|
|
|
This attribute shows which device API is being created, for example,
|
|
"vfio-pci" for a PCI device.
|
|
|
|
* available_instances
|
|
|
|
This attribute shows 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 shows a human readable name.
|
|
|
|
* description
|
|
|
|
This attribute can show brief features/description of the type. This is an
|
|
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::
|
|
|
|
int vfio_pin_pages(struct vfio_device *device, dma_addr_t iova,
|
|
int npage, int prot, struct page **pages);
|
|
|
|
void vfio_unpin_pages(struct vfio_device *device, dma_addr_t iova,
|
|
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.
|
|
|
|
References
|
|
==========
|
|
|
|
1. See Documentation/driver-api/vfio.rst 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
|