Convenient Intel PPIN Reporting To Come With Linux 5.18
The Protected Processor Inventory Number (also sometimes referred to as the "Protected Processor Identification Number") is a number set at manufacturing time to uniquely identify a given processor. The PPIN can also be translated back to a particular fab and production run, which can be useful when diagnosing any defects. Intel previously submitted Linux patches for showing the PPIN when hitting MCE errors for server administrators to help track from which physical CPUs the problem(s) are occurring -- but that only prints when an error comes up... Now with Linux 5.18 the PPIN will be more easily accessible to server administrators.
The PPIN is found on Intel Xeon server processors going back to Ivy Bridge for uniquely tracking given physical CPUs, which can be useful within large organizations and data centers and especially within multi-socket servers. The change with Linux 5.18 is now allowing the PPIN to be read as part of the CPU topology. Previously the model specific register (MSR) for PPIN had to be read manually if wanting the data but with Linux 5.18+ the PPIN will also be found under /sys/devices/system/cpu/cpu*/topology. As this is a unique "serial number" for the processor, reading the PPIN via sysfs is restricted to those with root access.
AMD also has a PPIN for their processors with their Linux patches posted back in 2020. This PPIN sysfs reporting should work for AMD processors as well.
As part of other PPIN patches, the sysfs reporting was added to TIP's x86/cpu Git branch for staging until the Linux 5.18 merge window next month.
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