You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
81 lines
5.1 KiB
81 lines
5.1 KiB
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 |
|
|
+-------------------------------------------------------------+
|
|
|