[PATCH v4 05/15] Documentation: fpga: dfl: add descriptions for virtualization and new interfaces.

[Wu Hao]

This patch adds virtualization support description for DFL based
FPGA devices (based on PCIe SRIOV), and introductions to new
interfaces added by new dfl private feature drivers.

Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
Acked-by: Alan Tull <atull@xxxxxxxxxx>
---
 Documentation/fpga/dfl.txt | 101 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/Documentation/fpga/dfl.txt b/Documentation/fpga/dfl.txt
index 6df4621..a22631f 100644
--- a/Documentation/fpga/dfl.txt
+++ b/Documentation/fpga/dfl.txt
@@ -84,6 +84,8 @@ The following functions are exposed through ioctls:
  Get driver API version (DFL_FPGA_GET_API_VERSION)
  Check for extensions (DFL_FPGA_CHECK_EXTENSION)
  Program bitstream (DFL_FPGA_FME_PORT_PR)
+ Assign port to PF (DFL_FPGA_FME_PORT_ASSIGN)
+ Release port from PF (DFL_FPGA_FME_PORT_RELEASE)
 
 More functions are exposed through sysfs
 (/sys/class/fpga_region/regionX/dfl-fme.n/):
@@ -99,6 +101,10 @@ More functions are exposed through sysfs
      one FPGA device may have more than one port, this sysfs interface indicates
      how many ports the FPGA device has.
 
+ Global error reporting management (errors/)
+     error reporting sysfs interfaces allow user to read errors detected by the
+     hardware, and clear the logged errors.
+
 
 FIU - PORT
 ==========
@@ -139,6 +145,10 @@ More functions are exposed through sysfs:
  Read Accelerator GUID (afu_id)
      afu_id indicates which PR bitstream is programmed to this AFU.
 
+ Error reporting (errors/)
+     error reporting sysfs interfaces allow user to read port/afu errors
+     detected by the hardware, and clear the logged errors.
+
 
 DFL Framework Overview
 ======================
@@ -212,6 +222,97 @@ the compat_id exposed by the target FPGA region. This check is usually done by
 userspace before calling the reconfiguration IOCTL.
 
 
+FPGA virtualization - PCIe SRIOV
+================================
+This section describes the virtualization support on DFL based FPGA device to
+enable accessing an accelerator from applications running in a virtual machine
+(VM). This section only describes the PCIe based FPGA device with SRIOV support.
+
+Features supported by the particular FPGA device are exposed through Device
+Feature Lists, as illustrated below:
+
+  +-------------------------------+  +-------------+
+  |              PF               |  |     VF      |
+  +-------------------------------+  +-------------+
+      ^            ^         ^              ^
+      |            |         |              |
++-----|------------|---------|--------------|-------+
+|     |            |         |              |       |
+|  +-----+     +-------+ +-------+      +-------+   |
+|  | FME |     | Port0 | | Port1 |      | Port2 |   |
+|  +-----+     +-------+ +-------+      +-------+   |
+|                  ^         ^              ^       |
+|                  |         |              |       |
+|              +-------+ +------+       +-------+   |
+|              |  AFU  | |  AFU |       |  AFU  |   |
+|              +-------+ +------+       +-------+   |
+|                                                   |
+|            DFL based FPGA PCIe Device             |
++---------------------------------------------------+
+
+FME is always accessed through the physical function (PF).
+
+Ports (and related AFUs) are accessed via PF by default, but could be exposed
+through virtual function (VF) devices via PCIe SRIOV. Each VF only contains
+1 Port and 1 AFU for isolation. Users could assign individual VFs (accelerators)
+created via PCIe SRIOV interface, to virtual machines.
+
+The driver organization in virtualization case is illustrated below:
+
+  +-------++------++------+             |
+  | FME   || FME  || FME  |             |
+  | FPGA  || FPGA || FPGA |             |
+  |Manager||Bridge||Region|             |
+  +-------++------++------+             |
+  +-----------------------+  +--------+ |             +--------+
+  |          FME          |  |  AFU   | |             |  AFU   |
+  |         Module        |  | Module | |             | Module |
+  +-----------------------+  +--------+ |             +--------+
+        +-----------------------+       |       +-----------------------+
+        | FPGA Container Device |       |       | FPGA Container Device |
+        |  (FPGA Base Region)   |       |       |  (FPGA Base Region)   |
+        +-----------------------+       |       +-----------------------+
+          +------------------+          |         +------------------+
+          | FPGA PCIE Module |          | Virtual | FPGA PCIE Module |
+          +------------------+   Host   | Machine +------------------+
+ -------------------------------------- | ------------------------------
+           +---------------+            |          +---------------+
+           | PCI PF Device |            |          | PCI VF Device |
+           +---------------+            |          +---------------+
+
+FPGA PCIe device driver is always loaded first once a FPGA PCIe PF or VF device
+is detected. It:
+
+	a) finish enumeration on both FPGA PCIe PF and VF device using common
+	   interfaces from DFL framework.
+	b) supports SRIOV.
+
+The FME device driver plays a management role in this driver architecture, it
+provides ioctls to release Port from PF and assign Port to PF. After release
+a port from PF, then it's safe to expose this port through a VF via PCIe SRIOV
+sysfs interface.
+
+To enable accessing an accelerator from applications running in a VM, the
+respective AFU's port needs to be assigned to a VF using the following steps:
+
+	a) The PF owns all AFU ports by default. Any port that needs to be
+	   reassigned to a VF must first be released through the
+	   DFL_FPGA_FME_PORT_RELEASE ioctl on the FME device.
+
+	b) Once N ports are released from PF, then user can use command below
+	   to enable SRIOV and VFs. Each VF owns only one Port with AFU.
+
+	   echo N > $PCI_DEVICE_PATH/sriov_numvfs
+
+	c) Pass through the VFs to VMs
+
+	d) The AFU under VF is accessible from applications in VM (using the
+	   same driver inside the VF).
+
+Note that an FME can't be assigned to a VF, thus PR and other management
+functions are only available via the PF.
+
+
 Device enumeration
 ==================
 This section introduces how applications enumerate the fpga device from
-- 
1.8.3.1