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author | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-06-12 14:52:51 -0300 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2019-06-14 14:23:26 -0600 |
commit | 09bbf055c3329008522b4a9814afe412c202daa7 (patch) | |
tree | de05ab653afce74b83e51e0b5142be1164e80ad0 /Documentation/mic/mic_overview.rst | |
parent | d67297ad343ec02a88f947b45526c92d2870aed3 (diff) | |
download | linux-stable-09bbf055c3329008522b4a9814afe412c202daa7.tar.gz linux-stable-09bbf055c3329008522b4a9814afe412c202daa7.tar.bz2 linux-stable-09bbf055c3329008522b4a9814afe412c202daa7.zip |
docs: mic: convert docs to ReST and rename to *.rst
Convert Intel Many Integrated Core architecture docs to ReST.
The conversion is trivial: just add title and literal block
markups, and adjust some identation.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/mic/mic_overview.rst')
-rw-r--r-- | Documentation/mic/mic_overview.rst | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/Documentation/mic/mic_overview.rst b/Documentation/mic/mic_overview.rst new file mode 100644 index 000000000000..17d956bdaf7c --- /dev/null +++ b/Documentation/mic/mic_overview.rst @@ -0,0 +1,85 @@ +====================================================== +Intel Many Integrated Core (MIC) architecture overview +====================================================== + +An Intel MIC X100 device is a PCIe form factor add-in coprocessor +card based on the Intel Many Integrated Core (MIC) architecture +that runs a Linux OS. It is a PCIe endpoint in a platform and therefore +implements the three required standard address spaces i.e. configuration, +memory and I/O. The host OS loads a device driver as is typical for +PCIe devices. The card itself runs a bootstrap after reset that +transfers control to the card OS downloaded from the host driver. The +host driver supports OSPM suspend and resume operations. It shuts down +the card during suspend and reboots the card OS during resume. +The card OS as shipped by Intel is a Linux kernel with modifications +for the X100 devices. + +Since it is a PCIe card, it does not have the ability to host hardware +devices for networking, storage and console. We provide these devices +on X100 coprocessors thus enabling a self-bootable equivalent +environment for applications. A key benefit of our solution is that it +leverages the standard virtio framework for network, disk and console +devices, though in our case the virtio framework is used across a PCIe +bus. A Virtio Over PCIe (VOP) driver allows creating user space +backends or devices on the host which are used to probe virtio drivers +for these devices on the MIC card. The existing VRINGH infrastructure +in the kernel is used to access virtio rings from the host. The card +VOP driver allows card virtio drivers to communicate with their user +space backends on the host via a device page. Ring 3 apps on the host +can add, remove and configure virtio devices. A thin MIC specific +virtio_config_ops is implemented which is borrowed heavily from +previous similar implementations in lguest and s390. + +MIC PCIe card has a dma controller with 8 channels. These channels are +shared between the host s/w and the card s/w. 0 to 3 are used by host +and 4 to 7 by card. As the dma device doesn't show up as PCIe device, +a virtual bus called mic bus is created and virtual dma devices are +created on it by the host/card drivers. On host the channels are private +and used only by the host driver to transfer data for the virtio devices. + +The Symmetric Communication Interface (SCIF (pronounced as skiff)) is a +low level communications API across PCIe currently implemented for MIC. +More details are available at scif_overview.txt. + +The Coprocessor State Management (COSM) driver on the host allows for +boot, shutdown and reset of Intel MIC devices. It communicates with a COSM +"client" driver on the MIC cards over SCIF to perform these functions. + +Here is a block diagram of the various components described above. The +virtio backends are situated on the host rather than the card given better +single threaded performance for the host compared to MIC, the ability of +the host to initiate DMA's to/from the card using the MIC DMA engine and +the fact that the virtio block storage backend can only be on the host:: + + +----------+ | +----------+ + | Card OS | | | Host OS | + +----------+ | +----------+ + | + +-------+ +--------+ +------+ | +---------+ +--------+ +--------+ + | Virtio| |Virtio | |Virtio| | |Virtio | |Virtio | |Virtio | + | Net | |Console | |Block | | |Net | |Console | |Block | + | Driver| |Driver | |Driver| | |backend | |backend | |backend | + +---+---+ +---+----+ +--+---+ | +---------+ +----+---+ +--------+ + | | | | | | | + | | | |User | | | + | | | |------|------------|--+------|------- + +---------+---------+ |Kernel | + | | | + +---------+ +---+----+ +------+ | +------+ +------+ +--+---+ +-------+ + |MIC DMA | | VOP | | SCIF | | | SCIF | | COSM | | VOP | |MIC DMA| + +---+-----+ +---+----+ +--+---+ | +--+---+ +--+---+ +------+ +----+--+ + | | | | | | | + +---+-----+ +---+----+ +--+---+ | +--+---+ +--+---+ +------+ +----+--+ + |MIC | | VOP | |SCIF | | |SCIF | | COSM | | VOP | | MIC | + |HW Bus | | HW Bus| |HW Bus| | |HW Bus| | Bus | |HW Bus| |HW Bus | + +---------+ +--------+ +--+---+ | +--+---+ +------+ +------+ +-------+ + | | | | | | | + | +-----------+--+ | | | +---------------+ | + | |Intel MIC | | | | |Intel MIC | | + | |Card Driver | | | | |Host Driver | | + +---+--------------+------+ | +----+---------------+-----+ + | | | + +-------------------------------------------------------------+ + | | + | PCIe Bus | + +-------------------------------------------------------------+ |