CSE-release/README.md

Overview

CXL Switch Emulator (CSE) is a software application that emulates the management path functionality of a CXL switch. It is compliant with the CXL Fabric Management API of the CXL 2.0 specification. All CXL FM management commands are sent using MCTP.

CSE listens for connections from a Fabric Manager (FM) over TCP on a default port of 2508. Only one remote connection is supported at a time. After a connection is terminated by the remote Fabric Manager, CSE will wait for another connection.

Supported Operating System Versions

• Ubuntu 23.10
• Fedora 38, 39

Note: Ubuntu 22.04 is not supported. This is due to some newer PCI features that are missing from the 5.15 Linux kernel that ships with Ubuntu 22.04.

Building

1. Install OS libraries

Install the following build packages to compile the software on the following operating systems.

Ubuntu:

apt install build-essential libglib2.0-dev libyaml-dev libpci-dev

Fedora:

2. Build Dependencies

To clone and build dependencies run:

./builddeps.bash

3. Build

After building the required dependencies run:

make

Usage

1. Create host directory for memory mapped files

CSE primarily emulates the management path functionality of a CXL switch and does not emulate PCIe/CXL data path functionality. However, some CXL FM API management commands enable the Fabric Manager to read or write to the memory space of CXL Type-3 devices. To emulate these commands, CSE can be configured to instantiate memory mapped files as backing stores. This will allow a Fabric Manager such as Jack to write to an arbitrary location in the memory space of a CXL Type-3 device, and then read back the contents of those locations.

If the user does not wish to use the CXL LD CXL.io Memory Request commands, this step can be skipped.

The config.yaml file has a parameter that specifies the location of a folder in the host file system where the memory mapped files will be located. The default location is /cxl. This directory must exist if the user plans to use the CXL LD CXL.io commands.

While the target directory (e.g. /cxl) can reside on the root file system of the host, it is recommended to use a tmpfs file system which can be created with the following command:

sudo mkdir /cxl 
sudo mount -t tmpfs -o size=4G,mode=1777 cxl /cxl 

This should be performed before starting the CSE application.

The capacity of the tmpfs file system is dependent up on how much of the CXL Type-3 device memory space needs to be written/read. The memory mapped files are sparse allocated and will only consume the actually written capacity on the tmpfs file system.

Note: memory mapped files are only created for virtual CXL device profiles that have a mmap: 1 in their profile definition in the config.yaml file.

2. Start the CSE application

The CSE application can be launched with the following command:

cse -lc config.yaml

The -l flag will configure CSE to produce log level output that states the commands received and actions taken.

3. Exit

To exit the application, type CTRL-C.