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X-OriginatorOrg: xilinx.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Nov 2021 22:24:39.3305 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fab5266e-83be-42ec-beaf-08d9abab605e X-MS-Exchange-CrossTenant-Id: 657af505-d5df-48d0-8300-c31994686c5c X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=657af505-d5df-48d0-8300-c31994686c5c;Ip=[149.199.62.198];Helo=[xsj-pvapexch01.xlnx.xilinx.com] X-MS-Exchange-CrossTenant-AuthSource: DM3NAM02FT053.eop-nam02.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR02MB6551 Precedence: bulk List-ID: X-Mailing-List: linux-fpga@vger.kernel.org Describe XRT driver architecture and provide basic overview of Xilinx Alveo platform. Signed-off-by: Sonal Santan Signed-off-by: Max Zhen Signed-off-by: Lizhi Hou --- Documentation/fpga/index.rst | 1 + Documentation/fpga/xrt.rst | 510 +++++++++++++++++++++++++++++++++++ MAINTAINERS | 10 + 3 files changed, 521 insertions(+) create mode 100644 Documentation/fpga/xrt.rst diff --git a/Documentation/fpga/index.rst b/Documentation/fpga/index.rst index f80f95667ca2..30134357b70d 100644 --- a/Documentation/fpga/index.rst +++ b/Documentation/fpga/index.rst @@ -8,6 +8,7 @@ fpga :maxdepth: 1 dfl + xrt .. only:: subproject and html diff --git a/Documentation/fpga/xrt.rst b/Documentation/fpga/xrt.rst new file mode 100644 index 000000000000..323ded5c0f4a --- /dev/null +++ b/Documentation/fpga/xrt.rst @@ -0,0 +1,510 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================== +XRTV2 Linux Kernel Driver Overview +================================== + +Authors: + +* Sonal Santan +* Max Zhen +* Lizhi Hou + +XRTV2 drivers are second generation `XRT `_ +drivers which support `Alveo `_ +PCIe platforms from Xilinx. + +XRTV2 drivers support *subsystem* style data driven platforms where driver's +configuration and behavior are determined by metadata provided by the platform +(in *device tree* format). Primary management physical function (MPF) driver +is called **xrt-mgmt**. Primary user physical function (UPF) driver is called +**xrt-user** and is under development. xrt_driver framework and FPGA subsystem +drivers are packaged into a library module called **xrt-lib**, which is shared +by **xrt-mgmt** and **xrt-user** (under development). The xrt_driver framework +implements a ``bus_type`` called **xrt_bus_type** which is used to discover HW +subsystems and facilitate inter HW subsystem interaction. + +Driver Modules +============== + +xrt-lib.ko +---------- + +xrt-lib is the repository of xrt drivers and pure software modules that can +potentially be shared between xrt-mgmt and xrt-user. All these drivers are +structured as **xrt_driver** and are instantiated by xrt-mgmt (or xrt-user under +development) based on the metadata associated with the hardware. The metadata +is in the form of a device tree as mentioned before. + +xrt-lib relies on OF kernel APIs to unflatten the metadata and overlay the +unflattened device tree nodes to system device tree. In xrt-lib module initialization +routine, "/xrt-bus" is created in system device tree, all XRT device +tree nodes and properties will be under "/xrt-bus". + +The xrt-lib infrastructure provides hooks to xrt_drivers for device node +management, user file operations and ioctl callbacks. The core infrastructure also +provides a bus functionality called **xrt_bus_type** for xrt_driver registration, +discovery and inter xrt_driver calls. xrt-lib does not have any dependency on PCIe +subsystem. + +xrt-mgmt.ko +------------ + +The xrt-mgmt driver is a PCIe device driver driving MPF found on Xilinx's Alveo +PCIe device. It creates one or more *group* device and one or more *xleaf* device. +The group and xleaf drivers are in xrt-lib and instantiations of the xrt_driver but +are called group and xleaf to symbolize the logical operation performed by them. + +The xrt-mgmt driver uses xrt-lib APIs to manages the life cycle of multiple group +drivers, which, in turn, manages multiple xleaf drivers. This flexibility allows +xrt-mgmt.ko and xrt-lib.ko to support various HW subsystems exposed by different +Alveo shells. The differences among these Alveo shells is handled in xleaf drivers. +The group driver is part of the infrastructure which provides common services to xleaf +drivers found on various Alveo shells. See :ref:`alveo_platform_overview`. + +The instantiation of specific group driver or xleaf drivers is completely data +driven based on metadata (mostly in device tree format) found through VSEC +capability and inside the firmware files, such as platform xsabin or user xclbin +file. + + +Driver Object Model +=================== + +The driver object model looks like the following:: + + +-----------+ + | of root | + +-----+-----+ + | + +---------+---------+ + | | + +-----------+ +----------+ + | xrt-bus | | ... | + +-----+-----+ +----------+ + | + +-----------+-----------+ + | | + v v + +-----------+ +-----------+ + | group | ... | group | + +-----+-----+ +------+----+ + | | + | | + +-----+----+ +-----+----+ + | | | | + v v v v + +-------+ +-------+ +-------+ +-------+ + | xleaf |..| xleaf | | xleaf |..| xleaf | + +-------+ +-------+ +-------+ +-------+ + +As an example, for Xilinx Alveo U50 before user xclbin download, the tree +looks like the following:: + + +-----------+ + | xrt-bus | + +-----+-----+ + | + +-------------------------+--------------------+ + | | | + v v v + +--------+ +--------+ +--------+ + | group0 | | group1 | | group2 | + +----+---+ +----+---+ +---+----+ + | | | + | | | + +-----+-----+ +----+-----+---+ +-----+-----+----+--------+ + | | | | | | | | | + v v | v v | v v | + +------------+ +------+ | +------+ +------+ | +------+ +-----------+ | + | xmgmt_main | | VSEC | | | GPIO | | QSPI | | | CMC | | AXI-GATE0 | | + +------------+ +------+ | +------+ +------+ | +------+ +-----------+ | + | +---------+ | +------+ +-----------+ | + +>| MAILBOX | +->| ICAP | | AXI-GATE1 |<+ + +---------+ | +------+ +-----------+ + | +-------+ + +->| CALIB | + +-------+ + +After a xclbin is downloaded, group3 will be added and the tree looks like the +following:: + + +-----------+ + | xrt-bus | + +-----+-----+ + | + +-------------------------+--------------------+-----------------+ + | | | | + v v v | + +--------+ +--------+ +--------+ | + | group0 | | group1 | | group2 | | + +----+---+ +----+---+ +---+----+ | + | | | | + | | | | + +-----+-----+ +-----+-----+---+ +-----+-----+----+--------+ | + | | | | | | | | | | + v v | v v | v v | | + +------------+ +------+ | +------+ +------+ | +------+ +-----------+ | | + | xmgmt_main | | VSEC | | | GPIO | | QSPI | | | CMC | | AXI-GATE0 | | | + +------------+ +------+ | +------+ +------+ | +------+ +-----------+ | | + | +---------+ | +------+ +-----------+ | | + +>| MAILBOX | +->| ICAP | | AXI-GATE1 |<+ | + +---------+ | +------+ +-----------+ | + | +-------+ | + +->| CALIB | | + +-------+ | + +---+----+ | + | group3 |<--------------------------------------------+ + +--------+ + | + | + +-------+--------+---+--+--------+------+-------+ + | | | | | | | + v | v | v | v + +--------+ | +--------+ | +--------+ | +-----+ + | CLOCK0 | | | CLOCK1 | | | CLOCK2 | | | UCS | + +--------+ v +--------+ v +--------+ v +-----+ + +-------------+ +-------------+ +-------------+ + | CLOCK-FREQ0 | | CLOCK-FREQ1 | | CLOCK-FREQ2 | + +-------------+ +-------------+ +-------------+ + + +group +----- + +The group driver represents a pseudo device whose life cycle is managed by +root and does not have real IO mem or IRQ resources. It's part of the +infrastructure of the MPF driver and resides in xrt-lib.ko. This driver + +* manages one or more xleaf drivers +* handle requests from xleaf drivers. For example event notifications and + inter xleaf calls. + +In xrt-mgmt, an initial group driver instance will be created by the PCIe driver. +This instance contains xleaf drivers that will trigger group instances to be +created to manage groups of xleaf drivers found on different partitions of +hardware, such as VSEC, Shell, and User. + +xleaf +----- + +The xleaf driver is a xrt_driver whose life cycle is managed by +a group driver and may or may not have real IO mem or IRQ resources. They +manage HW subsystems they are attached to. + +A xleaf driver without real hardware resources manages in-memory states for +xrt-mgmt. These states are shareable by other xleaf drivers. + +Xleaf drivers assigned to specific hardware resources drive a specific subsystem +in the device. To manipulate the subsystem or carry out a task, a xleaf driver +may ask for help from the root via root calls and/or from other leaves via +inter xleaf calls. + +A xleaf can also broadcast events through infrastructure code for other leaves +to process. It can also receive event notification from infrastructure about +certain events, such as post-creation or pre-exit of a particular xleaf. + +xrt_bus_type +------------ + +xrt_bus_type defines a virtual bus which handles xrt_driver probe, remove and match +operations. All xrt_drivers register with xrt_bus_type as part of xrt-lib driver +``module_init`` and un-register as part of xrt-lib driver ``module_exit``. + +FPGA Manager Interaction +======================== + +fpga_manager +------------ + +An instance of fpga_manager is created by xmgmt_main and is used for xclbin +image download. fpga_manager requires the full xclbin image before it can +start programming the FPGA configuration engine via Internal Configuration +Access Port (ICAP) xrt_driver. + +fpga_region +----------- + +For every interface exposed by the currently loaded xclbin/xsabin in the +*parent* fpga_region a new instance of fpga_region is created like a *child* +fpga_region. The device tree of the *parent* fpga_region defines the +resources for a new instance of fpga_bridge which isolates the parent from +child fpga_region. This new instance of fpga_bridge will be used when a +xclbin image is loaded on the child fpga_region. After the xclbin image is +downloaded to the fpga_region, an instance of a group is created for the +fpga_region using the device tree obtained as part of the xclbin. If this +device tree defines any child interfaces, it can trigger the creation of +fpga_bridge and fpga_region for the next region in the chain. + +fpga_bridge +----------- + +Like the fpga_region, an fpga_bridge is created by walking the device tree +of the parent group. The bridge is used for isolation between a parent and +its child. + +Driver Interfaces +================= + +xrt-mgmt Driver Ioctls +---------------------- + +Ioctls exposed by the xrt-mgmt driver to user space are enumerated in the +following table: + +== ===================== ============================ ========================== +# Functionality ioctl request code data format +== ===================== ============================ ========================== +1 FPGA image download XMGMT_IOCICAPDOWNLOAD_AXLF xmgmt_ioc_bitstream_axlf +== ===================== ============================ ========================== + +A user xclbin can be downloaded by using the xbmgmt tool from the XRT open source +suite. See example usage below:: + + xbmgmt partition --program --path /lib/firmware/xilinx/862c7020a250293e32036f19956669e5/test/verify.xclbin --force + +.. _alveo_platform_overview: + +Alveo Platform Overview +======================= + +Alveo platforms are architected as two physical FPGA partitions: *Shell* and +*User*. The Shell provides basic infrastructure for the Alveo platform like +PCIe connectivity, board management, Dynamic Function Exchange (DFX), sensors, +clocking, reset, and security. DFX, partial reconfiguration, is responsible for +loading the user compiled FPGA binary. + +For DFX to work properly, physical partitions require strict HW compatibility +with each other. Every physical partition has two interface UUIDs: the *parent* +UUID and the *child* UUID. For simple single stage platforms, Shell → User forms +the parent child relationship. + +.. note:: + Partition compatibility matching is a key design component of the Alveo platforms + and XRT. Partitions have child and parent relationship. A loaded partition + exposes child partition UUID to advertise its compatibility requirement. When + loading a child partition, the xrt-mgmt driver matches the parent + UUID of the child partition against the child UUID exported by the parent. + The parent and child partition UUIDs are stored in the *xclbin* (for the user) + and the *xsabin* (for the shell). Except for the root UUID exported by VSEC, + the hardware itself does not know about the UUIDs. The UUIDs are stored in + xsabin and xclbin. The image format has a special node called Partition UUIDs + which define the compatibility UUIDs. + + +The physical partitions and their loading are illustrated below:: + + SHELL USER + +-----------+ +-------------------+ + | | | | + | VSEC UUID | CHILD PARENT | LOGIC UUID | + | o------->|<--------o | + | | UUID UUID | | + +-----+-----+ +--------+----------+ + | | + . . + | | + +---+---+ +------+--------+ + | POR | | USER COMPILED | + | FLASH | | XCLBIN | + +-------+ +---------------+ + + +Loading Sequence +---------------- + +The Shell partition is loaded from flash at system boot time. It establishes the +PCIe link and exposes two physical functions to the BIOS. After the OS boots, +the xrt-mgmt driver attaches to the PCIe physical function 0 exposed by the Shell +and then looks for VSEC in the PCIe extended configuration space. Using VSEC, it +determines the logic UUID of the Shell and uses the UUID to load matching *xsabin* +file from Linux firmware directory. The xsabin file contains the metadata to +discover the peripherals that are part of the Shell and the firmware for any +embedded soft processors in the Shell. The xsabin file also contains Partition +UUIDs. + +The Shell exports a child interface UUID which is used for the compatibility +check when loading the user compiled xclbin over the User partition as part of DFX. +When a user requests loading of a specific xclbin, the xrt-mgmt driver reads +the parent interface UUID specified in the xclbin and matches it with the child +interface UUID exported by the Shell to determine if the xclbin is compatible with +the Shell. If the match fails, loading of xclbin is denied. + +xclbin loading is requested using the ICAP_DOWNLOAD_AXLF ioctl command. When loading +a xclbin, the xrt-mgmt driver performs the following *logical* operations: + +1. Copy xclbin from user to kernel memory +2. Sanity check the xclbin contents +3. Isolate the User partition +4. Download the bitstream using the FPGA config engine (ICAP) +5. De-isolate the User partition +6. Program the clocks (ClockWiz) driving the User partition +7. Wait for the memory controller (MIG) calibration +8. Return the loading status back to the caller + +`Platform Loading Overview `_ +provides more detailed information on platform loading. + + +xsabin +------ + +Each Alveo platform comes packaged with its own xsabin. The xsabin is a trusted +component of the platform. For format details refer to :ref:`xsabin_xclbin_container_format` +below. xsabin contains basic information like UUIDs, platform name and metadata in the +form of device tree. See :ref:`device_tree_usage` below for details and example. + +xclbin +------ + +xclbin is compiled by end user using +`Vitis `_ +tool set from Xilinx. The xclbin contains sections describing user compiled +acceleration engines/kernels, memory subsystems, clocking information etc. It also +contains an FPGA bitstream for the user partition, UUIDs, platform name, etc. + + +.. _xsabin_xclbin_container_format: + +xsabin/xclbin Container Format +------------------------------ + +xclbin/xsabin is ELF-like binary container format. It is structured as series of +sections. There is a file header followed by several section headers which is +followed by sections. A section header points to an actual section. There is an +optional signature at the end. The format is defined by the header file ``xclbin.h``. +The following figure illustrates a typical xclbin:: + + + +---------------------+ + | | + | HEADER | + +---------------------+ + | SECTION HEADER | + | | + +---------------------+ + | ... | + | | + +---------------------+ + | SECTION HEADER | + | | + +---------------------+ + | SECTION | + | | + +---------------------+ + | ... | + | | + +---------------------+ + | SECTION | + | | + +---------------------+ + | SIGNATURE | + | (OPTIONAL) | + +---------------------+ + + +xclbin/xsabin files can be packaged, un-packaged and inspected using an XRT +utility called **xclbinutil**. xclbinutil is part of the XRT open source +software stack. The source code for xclbinutil can be found at +https://github.com/Xilinx/XRT/tree/master/src/runtime_src/tools/xclbinutil + +For example, to enumerate the contents of a xclbin/xsabin use the *--info* switch +as shown below:: + + + xclbinutil --info --input /opt/xilinx/firmware/u50/gen3x16-xdma/blp/test/bandwidth.xclbin + xclbinutil --info --input /lib/firmware/xilinx/862c7020a250293e32036f19956669e5/partition.xsabin + + +.. _device_tree_usage: + +Device Tree Usage +----------------- + +The xsabin file stores metadata which advertise HW subsystems present in a +partition. The metadata is stored in device tree format with a well defined +schema. XRT management driver uses this information to create *xrt_devices* and +bind *xrt_drivers* to them. The xrt_drivers could be independent modules or +found in **xrt-lib.ko** kernel module. + +Deployment Models +================= + +Baremetal +--------- + +In bare-metal deployments, both MPF and UPF are visible and accessible. The +xrt-mgmt driver binds to MPF. The xrt-mgmt driver operations are privileged and +available to system administrator. The full stack is illustrated below:: + + HOST + + [XRT-MGMT] [XRT-USER] + | | + | | + +-----+ +-----+ + | MPF | | UPF | + | | | | + | PF0 | | PF1 | + +--+--+ +--+--+ + ......... ^................. ^.......... + | | + | PCIe DEVICE | + | | + +--+------------------+--+ + | SHELL | + | | + +------------------------+ + | USER | + | | + | | + | | + | | + +------------------------+ + + + +Virtualized +----------- + +In virtualized deployments, the privileged MPF is assigned to the host but the +unprivileged UPF is assigned to a guest VM via PCIe pass-through. The xrt-mgmt +driver in host binds to MPF. The xrt-mgmt driver operations are privileged and +only accessible to the MPF. The full stack is illustrated below:: + + + .............. + HOST . VM . + . . + [XRT-MGMT] . [XRT-USER] . + | . | . + | . | . + +-----+ . +-----+ . + | MPF | . | UPF | . + | | . | | . + | PF0 | . | PF1 | . + +--+--+ . +--+--+ . + ......... ^................. ^.......... + | | + | PCIe DEVICE | + | | + +--+------------------+--+ + | SHELL | + | | + +------------------------+ + | USER | + | | + | | + | | + | | + +------------------------+ + + + + + +Platform Security Considerations +================================ + +`Security of Alveo Platform `_ +discusses the deployment options and security implications in great detail. diff --git a/MAINTAINERS b/MAINTAINERS index 80eebc1d9ed5..fd7053bcfdb0 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7369,6 +7369,16 @@ F: Documentation/fpga/ F: drivers/fpga/ F: include/linux/fpga/ +FPGA XRT DRIVERS +M: Lizhi Hou +R: Max Zhen +R: Sonal Santan +L: linux-fpga@vger.kernel.org +S: Supported +W: https://github.com/Xilinx/XRT +F: Documentation/fpga/xrt.rst +F: drivers/fpga/xrt/ + FPU EMULATOR M: Bill Metzenthen S: Maintained