Merge tag 'docs-5.7' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "This has been a busy cycle for documentation work.

  Highlights include:

   - Lots of RST conversion work by Mauro, Daniel ALmeida, and others.
     Maybe someday we'll get to the end of this stuff...maybe...

   - Some organizational work to bring some order to the core-api
     manual.

   - Various new docs and additions to the existing documentation.

   - Typo fixes, warning fixes, ..."

* tag 'docs-5.7' of git://git.lwn.net/linux: (123 commits)
  Documentation: x86: exception-tables: document CONFIG_BUILDTIME_TABLE_SORT
  MAINTAINERS: adjust to filesystem doc ReST conversion
  docs: deprecated.rst: Add BUG()-family
  doc: zh_CN: add translation for virtiofs
  doc: zh_CN: index files in filesystems subdirectory
  docs: locking: Drop :c:func: throughout
  docs: locking: Add 'need' to hardirq section
  docs: conf.py: avoid thousands of duplicate label warning on Sphinx
  docs: prevent warnings due to autosectionlabel
  docs: fix reference to core-api/namespaces.rst
  docs: fix pointers to io-mapping.rst and io_ordering.rst files
  Documentation: Better document the softlockup_panic sysctl
  docs: hw-vuln: tsx_async_abort.rst: get rid of an unused ref
  docs: perf: imx-ddr.rst: get rid of a warning
  docs: filesystems: fuse.rst: supress a Sphinx warning
  docs: translations: it: avoid duplicate refs at programming-language.rst
  docs: driver.rst: supress two ReSt warnings
  docs: trace: events.rst: convert some new stuff to ReST format
  Documentation: Add io_ordering.rst to driver-api manual
  Documentation: Add io-mapping.rst to driver-api manual
  ...

1 files changed, 108 insertions, 0 deletions

diff --git a/Documentation/misc-devices/mic/scif_overview.rst b/Documentation/misc-devices/mic/scif_overview.rst
new file mode 100644
index 000000000000..4c8ad9e43706
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+++ b/Documentation/misc-devices/mic/scif_overview.rst
@@ -0,0 +1,108 @@
+========================================
+Symmetric Communication Interface (SCIF)
+========================================
+
+The Symmetric Communication Interface (SCIF (pronounced as skiff)) is a low
+level communications API across PCIe currently implemented for MIC. Currently
+SCIF provides inter-node communication within a single host platform, where a
+node is a MIC Coprocessor or Xeon based host. SCIF abstracts the details of
+communicating over the PCIe bus while providing an API that is symmetric
+across all the nodes in the PCIe network. An important design objective for SCIF
+is to deliver the maximum possible performance given the communication
+abilities of the hardware. SCIF has been used to implement an offload compiler
+runtime and OFED support for MPI implementations for MIC coprocessors.
+
+SCIF API Components
+===================
+
+The SCIF API has the following parts:
+
+1. Connection establishment using a client server model
+2. Byte stream messaging intended for short messages
+3. Node enumeration to determine online nodes
+4. Poll semantics for detection of incoming connections and messages
+5. Memory registration to pin down pages
+6. Remote memory mapping for low latency CPU accesses via mmap
+7. Remote DMA (RDMA) for high bandwidth DMA transfers
+8. Fence APIs for RDMA synchronization
+
+SCIF exposes the notion of a connection which can be used by peer processes on
+nodes in a SCIF PCIe "network" to share memory "windows" and to communicate. A
+process in a SCIF node initiates a SCIF connection to a peer process on a
+different node via a SCIF "endpoint". SCIF endpoints support messaging APIs
+which are similar to connection oriented socket APIs. Connected SCIF endpoints
+can also register local memory which is followed by data transfer using either
+DMA, CPU copies or remote memory mapping via mmap. SCIF supports both user and
+kernel mode clients which are functionally equivalent.
+
+SCIF Performance for MIC
+========================
+
+DMA bandwidth comparison between the TCP (over ethernet over PCIe) stack versus
+SCIF shows the performance advantages of SCIF for HPC applications and
+runtimes::
+
+             Comparison of TCP and SCIF based BW
+
+  Throughput (GB/sec)
+    8 +                                             PCIe Bandwidth ******
+      +                                                        TCP ######
+    7 +    **************************************             SCIF %%%%%%
+      |                       %%%%%%%%%%%%%%%%%%%
+    6 +                   %%%%
+      |                 %%
+      |               %%%
+    5 +              %%
+      |            %%
+    4 +           %%
+      |          %%
+    3 +         %%
+      |        %
+    2 +      %%
+      |     %%
+      |    %
+    1 +
+      +    ######################################
+    0 +++---+++--+--+-+--+--+-++-+--+-++-+--+-++-+-
+      1       10     100      1000   10000   100000
+                   Transfer Size (KBytes)
+
+SCIF allows memory sharing via mmap(..) between processes on different PCIe
+nodes and thus provides bare-metal PCIe latency. The round trip SCIF mmap
+latency from the host to an x100 MIC for an 8 byte message is 0.44 usecs.
+
+SCIF has a user space library which is a thin IOCTL wrapper providing a user
+space API similar to the kernel API in scif.h. The SCIF user space library
+is distributed @ https://software.intel.com/en-us/mic-developer
+
+Here is some pseudo code for an example of how two applications on two PCIe
+nodes would typically use the SCIF API::
+
+  Process A (on node A)			Process B (on node B)
+
+  /* get online node information */
+  scif_get_node_ids(..)			scif_get_node_ids(..)
+  scif_open(..)				scif_open(..)
+  scif_bind(..)				scif_bind(..)
+  scif_listen(..)
+  scif_accept(..)				scif_connect(..)
+  /* SCIF connection established */
+
+  /* Send and receive short messages */
+  scif_send(..)/scif_recv(..)		scif_send(..)/scif_recv(..)
+
+  /* Register memory */
+  scif_register(..)			scif_register(..)
+
+  /* RDMA */
+  scif_readfrom(..)/scif_writeto(..)	scif_readfrom(..)/scif_writeto(..)
+
+  /* Fence DMAs */
+  scif_fence_signal(..)			scif_fence_signal(..)
+
+  mmap(..)				mmap(..)
+
+  /* Access remote registered memory */
+
+  /* Close the endpoints */
+  scif_close(..)				scif_close(..)