Ahead of the Linux 7.3-rc4 kernel release due out in the coming hours, an important batch of x86/x86_64 fixes have been merged to address a few outstanding issues.

First up is a fix for Intel Xeon 6 "Granite Rapids" servers to avoid potentially problematic microcode that could lead to a machine check exception. Intel Granite Rapids microcode revision 0x1000405 brought internal changes that are needed for subsequent revisions. So there is now code in the Linux kernel to prevent loading 0x1000405 or later when the system hasn't been updated already to 0x1000405 for either early or late loading of the microcode. This change now merged to Linux 7.3 Git is also marked for back-porting to existing Linux kernel stable versions too.

On the specification update page it's listed as GNR98 for the MCE possibility with affected microcode versions. The disclosure attributes the internal changes to the inter-microcode communication interface. There is also GNR101 due to having an incorrect minimum runtime microcode update revision in Granite Rapid's 0x1000423 microcode version.

Also part of the x86 fixes is addressing Intel FRED on Panther Lake causing some games to crash or freeze when running under Wine / Steam Play.

There is also a fix over CONFIG_X86_NATIVE_CPU for "-march=native" compiler optimized kernel builds causing issues on upcoming Intel platforms with Advanced Performance Extensions (APX). The Linux kernel isn't yet ready to make use of the Extended General Purpose Registers (EGPRs) found with APX. But the native-optimized kernel builds is leading to R16 through R31 EGPR use with APX instructions and in turn causing havoc on Intel engineering systems. Thus the Linux kernel is now adapted when carrying out a native optimized kernel build to explicitly block APX/EGPR use until the kernel is ready to make use of APX functionality in-kernel.

More details on these now-merged x86 fixes for Linux 7.3-rc4 via this pull request.