Just before Linux 7.3-rc4 ships, a notable batch of x86/x86_64 fixes has been merged, targeting Intel Xeon 6 "Granite Rapids" microcode, FRED issues on Panther Lake, and upcoming APX extensions.
Granite Rapids microcode and MCE risk
For Intel Xeon 6 Granite Rapids servers, a serious corner case was found in microcode update 0x1000405. Internal changes in that revision can trigger a Machine Check Exception (MCE) if the system hasn’t already been updated to that exact version:
- The Linux kernel now blocks loading 0x1000405 or newer if the CPU wasn’t previously brought to 0x1000405;
- This applies to both early and late microcode loading paths;
- The patch is merged for Linux 7.3 and is also marked for stable backports.
In Intel’s spec update this issue appears as GNR98, attributed to the inter‑microcode communication interface. Another entry, GNR101, covers an incorrect minimum runtime microcode revision in Granite Rapids microcode 0x1000423.
FRED and game crashes under Wine / Steam Play
The x86 pull also includes a fix for Intel FRED on Panther Lake CPUs. A bug there caused some games to freeze or crash when run via Wine / Steam Play. The updated code adjusts FRED handling to restore stability for those titles.
APX, EGPRs and -march=native
A more forward‑looking fix targets CONFIG_X86_NATIVE_CPU and kernels built with -march=native on future Intel parts with Advanced Performance Extensions (APX) and Extended General Purpose Registers (EGPRs, R16–R31):
- The Linux kernel is not yet ready to use APX/EGPRs in‑kernel;
-march=nativewas causing the compiler to emit APX instructions and useR16–R31in some paths;- On Intel engineering systems this led to severe instability.
The kernel now explicitly disables APX/EGPR usage when doing a native‑optimized build, until proper in‑kernel APX support is implemented.
More technical details are available in the x86 pull request for Linux 7.3-rc4, which testers on desktop and server hardware will be picking up soon.
Source: Phoronix
