linux/Documentation/mic/mic_overview.txt
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   1An Intel MIC X100 device is a PCIe form factor add-in coprocessor
   2card based on the Intel Many Integrated Core (MIC) architecture
   3that runs a Linux OS. It is a PCIe endpoint in a platform and therefore
   4implements the three required standard address spaces i.e. configuration,
   5memory and I/O. The host OS loads a device driver as is typical for
   6PCIe devices. The card itself runs a bootstrap after reset that
   7transfers control to the card OS downloaded from the host driver. The
   8host driver supports OSPM suspend and resume operations. It shuts down
   9the card during suspend and reboots the card OS during resume.
  10The card OS as shipped by Intel is a Linux kernel with modifications
  11for the X100 devices.
  12
  13Since it is a PCIe card, it does not have the ability to host hardware
  14devices for networking, storage and console. We provide these devices
  15on X100 coprocessors thus enabling a self-bootable equivalent environment
  16for applications. A key benefit of our solution is that it leverages
  17the standard virtio framework for network, disk and console devices,
  18though in our case the virtio framework is used across a PCIe bus.
  19
  20MIC PCIe card has a dma controller with 8 channels. These channels are
  21shared between the host s/w and the card s/w. 0 to 3 are used by host
  22and 4 to 7 by card. As the dma device doesn't show up as PCIe device,
  23a virtual bus called mic bus is created and virtual dma devices are
  24created on it by the host/card drivers. On host the channels are private
  25and used only by the host driver to transfer data for the virtio devices.
  26
  27Here is a block diagram of the various components described above. The
  28virtio backends are situated on the host rather than the card given better
  29single threaded performance for the host compared to MIC, the ability of
  30the host to initiate DMA's to/from the card using the MIC DMA engine and
  31the fact that the virtio block storage backend can only be on the host.
  32
  33                                      |
  34               +----------+           |             +----------+
  35               | Card OS  |           |             | Host OS  |
  36               +----------+           |             +----------+
  37                                      |
  38        +-------+ +--------+ +------+ | +---------+  +--------+ +--------+
  39        | Virtio| |Virtio  | |Virtio| | |Virtio   |  |Virtio  | |Virtio  |
  40        | Net   | |Console | |Block | | |Net      |  |Console | |Block   |
  41        | Driver| |Driver  | |Driver| | |backend  |  |backend | |backend |
  42        +-------+ +--------+ +------+ | +---------+  +--------+ +--------+
  43            |         |         |     |      |            |         |
  44            |         |         |     |User  |            |         |
  45            |         |         |     |------|------------|---------|-------
  46            +-------------------+     |Kernel +--------------------------+
  47                      |               |       | Virtio over PCIe IOCTLs  |
  48                      |               |       +--------------------------+
  49+-----------+         |               |                   |  +-----------+
  50| MIC DMA   |         |               |                   |  | MIC DMA   |
  51| Driver    |         |               |                   |  | Driver    |
  52+-----------+         |               |                   |  +-----------+
  53      |               |               |                   |        |
  54+---------------+     |               |                   |  +----------------+
  55|MIC virtual Bus|     |               |                   |  |MIC virtual Bus |
  56+---------------+     |               |                   |  +----------------+
  57      |               |               |                   |              |
  58      |   +--------------+            |            +---------------+     |
  59      |   |Intel MIC     |            |            |Intel MIC      |     |
  60      +---|Card Driver   |            |            |Host Driver    |     |
  61          +--------------+            |            +---------------+-----+
  62                      |               |                   |
  63             +-------------------------------------------------------------+
  64             |                                                             |
  65             |                    PCIe Bus                                 |
  66             +-------------------------------------------------------------+
  67