Linux

Linux 7.2 Seeds "Blackwell-Next": A Deep Dive into the nvgrace-gpu VFIO CXL DVSEC Change

Linux 7.2 Seeds "Blackwell-Next": A Deep Dive into the nvgrace-gpu VFIO CXL DVSEC Change

Linux 7.2’s VFIO pull request dropped a commit with a codename I hadn’t seen before: Blackwell-Next. A Phoronix post brought this to my attention - Linux 7.2 Begins Making Preparations For NVIDIA “Blackwell-Next” - which, on the face of it looks like a minor prep patch. It is — but it’s also a clean window into where NVIDIA is taking its CPU-coherent GPU stack, how CXL is quietly becoming the standard signaling interface for next-generation accelerators, and what that means if you’re building infrastructure or tooling on top of these platforms.

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Linux Kernel v7.1 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v7.1 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v7.1 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v7.1 includes 47 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware1
Bug Fixes5
Refactoring & Cleanup5
Testing1
Other35

The v7.1 CXL/DAX cycle is defined by three interlocking themes: laying the groundwork for Type 2 accelerator support, hardening the DAX/HMEM subsystem against a cluster of correctness bugs, and a focused refactoring of the region layer that splits a monolithic file into purpose-specific translation units. None of these is a headline splash feature on its own, but together they represent the kind of steady, unglamorous investment that makes the subsystem reliable enough to build production systems on.

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Linux Kernel v7.0 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v7.0 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v7.0 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v7.0 includes 73 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware3
Bug Fixes11
Refactoring & Cleanup9
Testing2
Other48

Linux v7.0 brings focused but meaningful progress to the CXL/DAX subsystem, with the headline work centered on platform-specific address translation. The cxl/atl subsystem gains AMD Zen5 support through the ACPI Platform Runtime Mechanism Table (PRMT), enabling hardware-assisted Host Physical Address (HPA) to System Physical Address (SPA) translation on AMD’s latest server platforms. This required scaffolding across several layers: EFI runtime services preparation in cxl/acpi, new translation callback hooks, decoder locking for address translation paths, and explicit disabling of these handlers when Normalized Addressing is active — a sign the translation infrastructure is maturing toward multi-vendor, multi-mode support.

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Linux Kernel v6.19 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v6.19 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v6.19 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v6.19 includes 31 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware1
Bug Fixes4
Refactoring & Cleanup5
Testing1
Documentation2
Other18

Linux v6.19 is a measured release for the CXL/DAX subsystem — 31 commits spread across correctness fixes, code hardening, and targeted new functionality. The headline addition is extended linear cache (ELC) region support: regions can now be flagged to indicate they carry an ELC mapping, a prerequisite for properly managing CXL memory that participates in CPU-side cache hierarchies. Alongside the feature itself, the release includes adjustments to how ELC failures are reported through cxl_acpi, and the HBIW platform-data guard that was accidentally dropped has been restored.

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Linux Kernel v6.18 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v6.18 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v6.18 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v6.18 includes 32 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware1
Bug Fixes4
Refactoring & Cleanup5
Testing2
Other20

The v6.18 kernel cycle for CXL/DAX is defined by two architectural threads running in parallel: hardening the address-translation stack and untangling port initialization from topology discovery. On the translation side, the new SPA-to-DPA region mapping infrastructure lands alongside a dedicated root-decoder ops structure that formalizes how the host physical address space is projected into CXL’s device physical address space — including XOR-interleaving math that was previously implicit. These foundations make region geometry computable and auditable in ways that earlier releases left to convention.

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Linux Kernel v6.17 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v6.17 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v6.17 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v6.17 includes 32 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware1
Bug Fixes6
Refactoring & Cleanup3
Other22

The v6.17 cycle for CXL and DAX is a consolidation release rather than a feature-heavy one, with 32 commits that reflect the subsystem maturing around correctness, specification compliance, and architectural hygiene. The most visible theme is alignment with CXL specification revision 3.2: the Common Event Record has been updated to match the new spec, the Memory Sparing Event Record gains kernel tracing support for the first time, and additional validity checks land for corrected volatile memory error (CVME) counts in both DRAM and General Media Event Records. This work strengthens the kernel’s ability to correctly interpret and surface CXL RAS events to userspace tooling and monitoring infrastructure.

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How to Build acpidump from Source and use it to Debug Complex CXL and PCI Issues

How to Build acpidump from Source and use it to Debug Complex CXL and PCI Issues

This article is a detailed guide on how to build the latest version of the acpidump tool from its source code. While many Linux distributions, like Ubuntu, offer a packaged version of this utility, it’s often outdated. For developers and enthusiasts working with modern hardware features, particularly those related to Compute Express Link (CXL), having the most current version is essential.

Before you begin, it’s important to remove any old, conflicting versions of the tools. If you have previously installed the acpica-tools package from your distribution’s repository, you should remove it to prevent conflicts.

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Linux Kernel v6.16 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v6.16 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v6.16 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v6.16 includes 37 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware2
Bug Fixes6
Refactoring & Cleanup8
Documentation3
Other18

The Linux v6.16 kernel cycle is dominated by one clear theme: hardening CXL memory device reliability and serviceability through the EDAC subsystem. Four new control features land in this release — patrol scrub, Error Check Scrub (ECS), soft Post Package Repair (PPR), and memory sparing — each exposing a distinct class of CXL 3.0 memory maintenance operations to userspace through a consistent sysfs interface. Alongside these, support for the PERFORM_MAINTENANCE command provides the underlying mechanism that drives scrub and repair operations on compliant devices. Taken together, this work moves CXL from a device class that Linux can merely enumerate and map to one where the kernel actively participates in proactive memory health management.

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Is Your Application Really Using Persistent Memory? Here’s How to Tell.

Is Your Application Really Using Persistent Memory? Here’s How to Tell.

Persistent memory (PMEM), especially when accessed via technologies like CXL, promises the best of both worlds: DRAM-like speed with the durability of an SSD. When you set up a filesystem like XFS or EXT4 in FSDAX (File System Direct Access) mode on a PMEM device, you’re paving a superhighway for your applications, allowing them to map files directly into their address space and bypass the kernel’s page cache entirely.

But here’s the crucial question: after all the setup and configuration, how do you prove that your application’s data is physically residing on the PMEM device and not just in regular RAM? I’ve run into this question myself, so I wrote a small Python script to get a definitive answer using SQLite3 as an example application. However, before we proceed with the script, let’s examine how you can verify this manually.

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How to Confirm Virtual to Physical Memory Mappings for PMem and FSDAX Files

How to Confirm Virtual to Physical Memory Mappings for PMem and FSDAX Files

Are you curious whether your application’s memory-mapped files are really using Intel Optane Persistent Memory (PMem), Compute Express Link (CXL) Non-Volatile Memory Modules (NV-CMM), or another DAX-enabled persistent memory device? Want to understand how virtual memory maps onto physical, non-volatile regions? Let’s use easily adaptable scripts in both Python and C to confirm this on your Linux system, definitively.

Why Does This Matter?

With the advent of persistent memory and DAX (Direct Access) filesystems, applications can memory-map files directly onto PMem, bypassing the traditional DRAM page cache. This promises significant performance and durability improvements for data-intensive workloads and databases, such as SQLite, Redis, and others.

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CXL Memory NUMA Node Mapping with Sub-NUMA Clustering (SNC) on Linux

CXL Memory NUMA Node Mapping with Sub-NUMA Clustering (SNC) on Linux

CXL (Compute Express Link) memory devices are revolutionizing server architectures, but they also introduce new NUMA complexity, especially when advanced memory configurations, such as Sub-NUMA Clustering (SNC), are enabled. One of the most confusing issues is the mismatch between NUMA node numbers reported by CXL sysfs attributes and those used by Linux memory management tools.

This blog post walks through a real-world scenario, complete with command outputs and diagrams, to help you understand and resolve the CXL NUMA node mapping issue with SNC enabled.

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Linux Kernel v6.15 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v6.15 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v6.15 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v6.15 includes 55 commits to the CXL and DAX subsystems:

CategoryCommits
New Features & Hardware6
Bug Fixes4
Performance1
Refactoring & Cleanup9
Other35

The Linux v6.15 kernel marks a meaningful expansion of CXL’s userspace interface story. The headline addition is FWCTL support: CXL devices can now expose get-feature and set-feature mailbox commands to userspace through the fwctl subsystem, giving operators and tooling a standardized RPC path to query and configure device-specific feature registers without requiring bespoke kernel drivers for each capability. This is the groundwork that enables feature negotiation at the management layer — expect CXL tooling to start consuming these interfaces quickly.

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Fastfetch: The Speedy Successor Neofetch Replacement Your Ubuntu Terminal Needs

Fastfetch: The Speedy Successor Neofetch Replacement Your Ubuntu Terminal Needs

If you love customizing your Linux terminal and getting a quick, visually appealing overview of your system specs, you might have used neofetch in the past. However, neofetch is now deprecated and no longer actively maintained. A fantastic, actively maintained alternative is Fastfetch – known for its speed, extensive customization options, and feature set.

While you might be able to install Fastfetch on Ubuntu 22.04 (Jammy Jellyfish) using the standard sudo apt install fastfetch, the version available in the default Ubuntu repositories is often outdated. To get the latest features, bug fixes, and performance improvements, you’ll want to use a different method.

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Linux Kernel 6.14 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel 6.14 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel 6.14 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Here is the detailed list of all commits merged into the 6.14 Kernel for CXL and DAX. This list was generated by the Linux Kernel CXL Feature Tracker .

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Linux Kernel v6.14 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel v6.14 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel v6.14 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Release Highlights

Linux Kernel v6.14 includes 13 commits to the CXL and DAX subsystems:

CategoryCommits
Bug Fixes1
Refactoring & Cleanup2
Other10

The dominant story in v6.14’s CXL changes is alignment with CXL specification revision 3.1 in the event subsystem. Five event record types — Common, General Media, DRAM, Memory Module, and Component Identifier — were updated to match the latest spec. These records are how CXL devices surface hardware faults, media errors, and performance anomalies to the host, so keeping them in sync with the specification is critical for accurate error classification and interoperability with newer hardware that implements the 3.1 format changes.

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Linux Kernel 6.13 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel 6.13 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel 6.13 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Here is the detailed list of all commits merged into the 6.13 Kernel for CXL and DAX. This list was generated by the Linux Kernel CXL Feature Tracker .

CXL related changes from Kernel v6.12 to v6.13:

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A Step-by-Step Guide on Using Cloud Images with QEMU 9 on Ubuntu 24.04

A Step-by-Step Guide on Using Cloud Images with QEMU 9 on Ubuntu 24.04

Introduction

Cloud images are pre-configured, optimized templates of operating systems designed specifically for cloud and virtualized environments. Cloud images are essentially vanilla operating system installations, such as Ubuntu, with the addition of the cloud-init package. This package enables run-time configuration of the OS through user data, such as text files on an ISO filesystem or cloud provider metadata. Using cloud images significantly reduces the time and effort required to set up a new virtual machine. Unlike ISO images, which require a full installation process, cloud images boot up immediately with the OS pre-installed

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Linux Kernel 6.10 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel 6.10 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel 6.10 release brings several improvements and additions related to Compute Express Link (CXL) technology.

Here is the detailed list of all commits merged into the 6.10 Kernel for CXL and DAX. This list was generated by the Linux Kernel CXL Feature Tracker .

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Linux Kernel 6.9 is Released: This is What's New for Compute Express Link (CXL)

Linux Kernel 6.9 is Released: This is What's New for Compute Express Link (CXL)

The Linux Kernel 6.9 release brings several improvements and additions related to Compute Express Link (CXL) technology.

New Features

Here is a list of new features for CXL:

Here is the detailed list of all commits merged into the 6.9 Kernel for CXL and DAX. This list was generated by the Linux Kernel CXL Feature Tracker .

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Linux Kernel CXL Feature Tracker

Linux Kernel CXL Feature Tracker

I’m always watching the Linux Kernel for new and exciting features that are merged for Compute Express Link (CXL). There’s some great notes from the monthly developer meetup here , but the devil is always in the details, and not every commit is discussed in the meeting. So I wrote a simple Python script, called cxl_feature_tracker.py that looks in all commits to the Linus Torvalds Linux Kernel GitHub repository , and extracts any that mention “CXL” or “DAX”, or that make changes to the drivers/cxl or drivers/dax directories. The output is a very long list, but it has some gems amongst the list of fixes.

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Using Linux Kernel Tiering with Compute Express Link (CXL) Memory

Using Linux Kernel Tiering with Compute Express Link (CXL) Memory

In this blog post, we will walk through the process of enabling the Linux Kernel Transparent Page Placement (TPP) feature with CXL memory mapped as NUMA nodes using the system-ram namespace. This feature allows the kernel to automatically place pages in different types of memory based on their usage patterns.

Prerequisites

This guide assumes that you are using a Fedora 36 system with Kernel 5.19.13, and that your system has a Samsung CXL device installed. You can confirm the presence of the CXL device with the following command:

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How To Install a Mainline Linux Kernel in Ubuntu

Note: This article was updated on Thursday, July 31st, 2025 and will work with newer Ubuntu releases.

By default, Ubuntu systems run with the Ubuntu kernels provided by the Ubuntu repositories. To get unmodified upstream kernels that have new features or to confirm that upstream has fixed a specific issue, we often need to install the mainline Kernel. The mainline kernel is the most recent version of the Linux kernel released by the Linux Kernel Organization. It undergoes several stages of development, including merge windows, release candidates, and final releases. Mainline kernels are designed to offer the latest features and improvements, making them attractive to developers and power users. Kernel.org lists the available Kernel versions.

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