RE: [PATCH 1/8] x86/microcode/intel: Reject problematic loading on GNR systems

[Van De Ven, Arjan]

> On 9/1/2026 4:16 PM, Chang S. Bae wrote:
> > Revision 0x1000405 contains internal microcode changes that are required
> > by subsequent revisions to avoid #MC during loading.
> 
> Before going to the solution space, can we add some more
> context/background here?

I think, taking as step back, the world is sort of simple and more examples maybe helping or maybe not.

At the request of "linux folks" (many on the CC), Intel added a "minrev" field for the microcode files, to express a "don't load this unless you are at least at version XYZ", for various compatibility reasons.

At the time, we added this as a check to "runtime" loading, but not during early loading. In hindsight this was a mistake, compatibility issues are not limited to late runtime loading, but can also happen during earlier-in-the-OS loading.

The example mentioned is a case where this became no longer theoretical.... 

Now, these kind of compat breaks are somewhat rare (we can debate what rare means I suppose), but clearly they happen (the bug mentioned is clear existence proof).

The more detailed nicer solution is in later patches -- this patch just makes the kernel honor the minrev field more consistently, which gets the kernel into a "safe" space again. The reason this patch is first is one of -stable backports. One can imagine that -stable folks like to take the most simple solution back first before even considering a more complex solution....