[RFC,v3,0/6] Add mdev (Mediated device) support in DPDK

Message ID 20210601030644.3318-1-chenbo.xia@intel.com (mailing list archive)


Chenbo Xia June 1, 2021, 3:06 a.m. UTC
  Hi everyone,

This is a draft implementation of the mdev (Mediated device [1])
support in DPDK PCI bus driver. Mdev is a way to virtualize devices
in Linux kernel. Based on the device-api (mdev_type/device_api),
there could be different types of mdev devices (e.g. vfio-pci).
In this patchset, the PCI bus driver is extended to support scanning
and probing the mdev devices whose device-api is "vfio-pci".

                     | PCI bus |
         |        |               |        |
  Physical PCI devices ...   Mediated PCI devices ...

The first four patches in this patchset are mainly preparation of mdev
bus support. The left two patches are the key implementation of mdev bus.

The implementation of mdev bus in DPDK has several options:

1: Embed mdev bus in current pci bus

   This patchset takes this option for an example. Mdev has several
   device types: pci/platform/amba/ccw/ap. DPDK currently only cares
   pci devices in all mdev device types so we could embed the mdev bus
   into current pci bus. Then pci bus with mdev support will scan/plug/
   unplug/.. not only normal pci devices but also mediated pci devices.

2: A new mdev bus that scans mediated pci devices and probes mdev driver to
   plug-in pci devices to pci bus

   If we took this option, a new mdev bus will be implemented to scan
   mediated pci devices and a new mdev driver for pci devices will be
   implemented in pci bus to plug-in mediated pci devices to pci bus.

   Our RFC v1 takes this option:

   Note that: for either option 1 or 2, device drivers do not know the
   implementation difference but only use structs/functions exposed by
   pci bus. Mediated pci devices are different from normal pci devices
   on: 1. Mediated pci devices use UUID as address but normal ones use BDF.
   2. Mediated pci devices may have some capabilities that normal pci
   devices do not have. For example, mediated pci devices could have
   regions that have sparse mmap capability, which allows a region to have
   multiple mmap areas. Another example is mediated pci devices may have
   regions/part of regions not mmaped but need to access them. Above
   difference will change the current ABI (i.e., struct rte_pci_device).
   Please check 5th and 6th patch for details.

3. A brand new mdev bus that does everything

   This option will implement a new and standalone mdev bus. This option
   does not need any changes in current pci bus but only needs some shared
   code (linux vfio part) in pci bus. Drivers of devices that support mdev
   will register itself as a mdev driver and do not rely on pci bus anymore.
   This option, IMHO, will make the code clean. The only potential problem
   may be code duplication, which could be solved by making code of linux
   vfio part of pci bus common and shared.

Your comments on above three options are welcomed and appreciated!


RFC v3:
- Add sparse mmap support
- Minor fixes and improvements

RFC v2:
- Let PCI bus scan mediated PCI devices directly
- Address Keith's comments
- Merge below patch into this series (David)
- Add internal representation of PCI device (David)
- Minor fixes and improvements

[1] https://github.com/torvalds/linux/blob/master/Documentation/driver-api/vfio-mediated-device.rst

Chenbo Xia (1):
  bus/pci: add sparse mmap support for mediated PCI devices

Tiwei Bie (5):
  bus/pci: introduce an internal representation of PCI device
  bus/pci: avoid depending on private value in kernel source
  bus/pci: introduce helper for MMIO read and write
  eal: add a helper for reading string from sysfs
  bus/pci: add mdev support

 drivers/bus/pci/bsd/pci.c             |  36 +-
 drivers/bus/pci/linux/pci.c           | 107 ++++-
 drivers/bus/pci/linux/pci_init.h      |  29 +-
 drivers/bus/pci/linux/pci_uio.c       |  22 +
 drivers/bus/pci/linux/pci_vfio.c      | 586 ++++++++++++++++++++++----
 drivers/bus/pci/linux/pci_vfio_mdev.c | 277 ++++++++++++
 drivers/bus/pci/meson.build           |   1 +
 drivers/bus/pci/pci_common.c          |  86 ++--
 drivers/bus/pci/pci_params.c          |  36 +-
 drivers/bus/pci/private.h             |  40 ++
 drivers/bus/pci/rte_bus_pci.h         |  83 +++-
 drivers/bus/pci/version.map           |   4 +
 lib/eal/common/eal_filesystem.h       |  10 +
 lib/eal/freebsd/eal.c                 |  22 +
 lib/eal/linux/eal.c                   |  39 +-
 lib/eal/version.map                   |   3 +
 16 files changed, 1224 insertions(+), 157 deletions(-)
 create mode 100644 drivers/bus/pci/linux/pci_vfio_mdev.c