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Announcing the Unbreakable Enterprise Kernel Release 6 Update 2 for Oracle Linux

Simon Coter
Senior Manager, Oracle Linux and Virtualization Product Management

The Unbreakable Enterprise Kernel (UEK) for Oracle Linux provides the latest open source innovations, key optimizations, and security to cloud and on-premises workloads. It is the Linux kernel that powers Oracle Cloud and Oracle Engineered Systems such as Oracle Exadata Database Machine and Oracle Linux on Intel/AMD as well as Arm platforms.

What's New?

The Unbreakable Enterprise Kernel Release 6 Update 2 (UEK R6U2) for Oracle Linux is based on the mainline kernel version 5.4. By actively monitoring upstream check-ins and collaboration with partners and customers, Oracle continues to improve and apply critical bug and security fixes to UEK R6. This update includes several new features, added functionality, and bug fixes across a range of subsystems.

UEK R6U2 can be recognized with a release number starting with 5.4-17-2102 and is an update to the upstream mainline kernel v5.4.83. UEK R6U2 includes upstream LTS bug fixes, with additional patches to enhance existing functionality and provide some minor bug fixes and security improvements.

Notable changes:

  • New Slab Memory Controller. The new slab memory controller specifically addresses the low slab utilization issue that existed in the previous design; this improvement is particularly beneficial for systems with a large number of memory cgroups. Note that upstream reports have indicated a 50% savings in slab memory usage, per the implementation of this feature.

  • vDPA driver for Mellanox ConnectX-6 Dx devices added. Support for the vHost Data Path Acceleration (vDPA) framework and Mellanox CX6-DX VDPA driver have been added in this update. When utilized on a host, for high performance, this feature provides Virtual I/O Device (VirtIO) acceleration. This functionality is implemented by the device's hardware, while preserving the ability to use standard VirtIO drivers on the virtual machines (VMs) that are running on the host.

  • NVMe improvements and changes. This update includes fixes for most of the bugs that were present in the 5.9 upstream kernel.

  • Improvements, bug and security fixes for Btrfs, CIFS, ext4, NFS, OCFS2, and XFS filesystems.

  • Drivers

    • Broadcom Emulex LightPulse Fibre Channel SCSI driver. lpfc driver has been updated to version With this update, a 256G/bit speed setting is enabled for SCSI Fibre Channel transport.

    • LSI MPT Fusion SAS 3.0 Device driver. mpt3sas has been updated to version, in line with the upstream kernel release.

    • QLogic Fibre Channel HBA driver. qla2xxx has been updated to version and includes a large number of vendor supplied patches and is in line with the upstream kernel release.

  • Enhanced Tech-Preview features

    • Core scheduling is a feature enabled in the kernel to limit trusted tasks to run concurrently on CPU cores that share compute resources, to help mitigate against certain categories of 'core shared cache' processor bugs that could cause data leakage and other related vulnerabilities. Core scheduling, introduced with UEK R6U1, is still under active development.

    • Wireguard is a faster and more secure replacement for IPsec and OpenVPN. New networks are being built with modern cryptography from WireGuard rather than legacy technologies like IPsec and OpenVPN. WireGuard, initially enabled as a technical preview in UEK R6U1, includes several improvements.

    • NFS v4.2 Server Side Copy functionality is back-ported from the upstream kernel and provides mechanisms that allow an NFS client to copy file data on a server or between two servers without the data being transmitted back and forth over the network through the NFS client. Introduced with UEK R6U1, several improvements are part of this release.

For details on these and other new features and changes, please consult the Release Notes for the UEK R6 Update 2.

Security (CVE) Fixes

A full list of CVEs fixed in this release can be found in the Release Notes for the UEK R6U2.

Software Download

Oracle Linux is free to download, use, and redistribute for an unlimited number of systems. This includes the ISO, updates, and errata – everything – in easy-to-use packaging.

We offer the same software regardless of whether you are using it for development or for production, with self-support or with an Oracle support subscription. Mix and match as much as you like, no limitations.

Customers with Oracle Linux Premier Support also receive access to zero-downtime kernel updates using Oracle Ksplice.


UEK R6 Update 2 is fully compatible with the UEK R6 GA release. The kernel ABI for UEK R6 remains unchanged in all subsequent updates to the initial release.


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