CXL Device Test Systems Using DAX Memory Isolation
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Solution Overview
Problem
Existing testing systems and methods for CXL protocol compliant devices face challenges such as memory corruption, interference during testing, and inefficient hot add/swapping, particularly when testing multiple devices in parallel, due to shared memory spaces and BIOS-dependent enumeration.
Innovation Solution
The implementation of a test system with a DAX interface that isolates CXL devices from memory corruption, allows hot add/swapping without system reboot, and manages parallel testing through separate memory ranges and DAX management, utilizing APIs for user-friendly interaction and efficient workload generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CXL DUTs are used in shared system memory mode, then memory resources are shared and accessible by multiple entities, but memory corruption and interference occur between devices
Solution Approach 1:
The patent divides the shared system memory space into separate per-device memory spaces for each CXL DUT. Each device is allocated its own isolated memory region, preventing other devices from accessing or corrupting its memory. This segmentation resolves the contradiction by maintaining shared memory capabilities while eliminating memory corruption through spatial separation of memory resources.
2Ease of operation
If traditional testing systems are used for CXL devices, then device enumeration is performed through BIOS, but hot add/swapping requires system reboot which wastes time
Solution Approach 1:
The patent implements a test system with a load board that can perform device enumeration and initialization actions before the device is fully integrated into the system. The load board pre-configures CXL devices and maintains their enumeration information, so when hot add/swapping occurs, the devices are already prepared and recognized without requiring a full system reboot. This preliminary action eliminates the time loss associated with reboots while maintaining ease of device management.
3Productivity
If multiple CXL DUTs are tested in parallel, then testing efficiency increases, but interference between testing operations occurs due to shared memory
Solution Approach 1:
The patent assigns separate per-device memory spaces to each CXL DUT being tested in parallel. Each device operates in its own isolated memory environment, preventing testing operations on one device from interfering with others. This segmentation enables true parallel testing where multiple devices can be tested simultaneously without mutual interference, thereby increasing productivity while eliminating harmful testing interference.
Solution Approach 2:
The load board acts as an intermediary between the test system and multiple CXL DUTs. It manages memory allocation and device enumeration for each DUT, ensuring that parallel testing operations are coordinated and isolated. The load board mediates access to memory resources, allowing multiple devices to be tested in parallel without interference by controlling and separating their respective memory spaces.
4Quantity of substance
If CXL devices are used for shared storage resources, then memory capacity is extended, but testing capabilities are limited by traditional ATE systems
Solution Approach 1:
The patent designs a load board with a DAX interface that serves multiple functions: it manages CXL device enumeration, allocates memory spaces, enables hot add/swapping, and supports parallel testing of multiple devices. This multi-functional load board provides comprehensive testing capabilities for CXL devices while maintaining their use as shared storage resources, thereby increasing adaptability without sacrificing memory capacity expansion.
Data Source
AI summary
Efficient and effective testing systems and methods are presented. In one embodiment, a test system includes: a user interface configured to enable user interaction with the system; a test board configured to communicatively couple with a plurality of devices under test (DUTs), wherein the DUTs are compute express link (CXL) protocol compliant; and a tester configured to direct testing of the plurality of DUTs, wherein the tester includes a direct access device (DAX) interface that prevents corruption of DUTs. In one exemplary implementation, the tester isolates testing of a particular CXL enabled DUT from undesirable interference and corruption. The tester can prevent inappropriate writing over the DUT's memory. The DUTs reside in the separate per-device space of a Linux operating system rather than an extension of memory space. One of the plurality of DUTs can be a CXL type 3 memory expander device. In one exemplary implementation, the direct access device (DAX) interface creates a unique DAX instance for each individual DUT included in the plurality of DUTs