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Subject[PATCH 05/15] Documentation: fpga: dfl: add descriptions for virtualization and new interfaces.
Date
From: Wu Hao <hao.wu@intel.com>

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.

[mdf@kernel.org: Fixed up to make it work with new reStructuredText docs]
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Wu Hao <hao.wu@intel.com>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
---
Documentation/fpga/dfl.rst | 100 +++++++++++++++++++++++++++++++++++++
1 file changed, 100 insertions(+)

diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
index 2f125abd777f..be9929dd7251 100644
--- a/Documentation/fpga/dfl.rst
+++ b/Documentation/fpga/dfl.rst
@@ -87,6 +87,8 @@ 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/):
@@ -143,6 +145,9 @@ More functions are exposed through sysfs:
Read Accelerator GUID (afu_id)
afu_id indicates which PR bitstream is programmed to this AFU.

+ Global error reporting management (errors/)
+ error reporting sysfs interfaces allow user to read errors detected by the
+ hardware, and clear the logged errors.

DFL Framework Overview
======================
@@ -218,6 +223,101 @@ 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:
+
+* Finishes enumeration on both FPGA PCIe PF and VF device using common
+ interfaces from DFL framework.
+* 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:
+
+#. 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.
+
+#. 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
+
+#. Pass through the VFs to VMs
+
+#. 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
--
2.22.0
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