A second candidate for Linux Kernel 5.10 will be released later today, but kernel maintainer Greg Kroah-Hartman issued a deferred request today, mainly due to the removal of Intel MIC (Integrated Crowd Core Architecture) drivers, including Xeon Phi.
Cleaning up Intel MIC drivers from the kernel streamlines nearly 27,000 lines of code. These codes are for Intel’s failed MIC X100 (Knights Corner and later), which originated from the earlier Larrabee project and is a PCIe-shaped coprocessor based on Intel’s integrated multi-core architecture. In Linux Kernel 5.10, all code that interfaces with these accelerators, once advertised as Xeon Phi, was removed.
Intel added MIC code in 2013 and has had a brief period of continuous improvement since then. Intel MIC code is about to be purged from Linux Kernel 5.10 after Intel’s CPU and GPU banned MIC/Xeon Phi for several years. It makes sense that these devices have been out of production for years, and Intel no longer wants to maintain the code, especially for hardware that has never been delivered on a large scale.
In today’s request to remove MIC, Greg Kroah-Hartman also noted that security researchers/kernel developers are beginning to see security issues with MIC driver code, “which is welcomed by many because the DMA use of these drivers is very interesting.” Security personnel are also beginning to question some of the issues that are beginning to be discovered in the code base. “
A MIC code base may be restored in the future. Greg points out that VOP (PCIe-based VirtIO) may be re-used for use by other PCI Express devices and added to the kernel at a later time. Intel VOP code addresses some of the PCI Express virtualization issues that affect other vendors, but is currently designed only for Intel hardware/drivers. Therefore, if this code works more broadly, the VOP section may re-appear in mainline in the future.