NACK/Cmnt: [SRU][R][PATCH 0/4] Take Intel platform into account for old microcode checks

[Rickey Castillo Valenzuela]

On 8/14/26 15:36, Michael Reed via kernel-team wrote:
> From: Michael Reed <Michael.Reed at canonical.com>
>
> SRU Justification
>
> [ Impact ]
>
> The issue is Intel added code to Linux to check for old microcode. They base it on some processor fields not realizing there are multiple processor SKUs with the same processor field information. The result is the Linux wrongly prints out "Running old microcode" and sets taint bit 2 for some processor SKUs.
> It takes specific Intel processor SKUs to hit the issue. This has been seen with Sapphire Rapids and Granite Rapids processors
>
> [ Fix ]
>
> These patches fix the issue
>
> 238be4ba x86/microcode: Refactor platform ID enumeration into a helper
> d8630b67 x86/cpu: Add platform ID to CPU info structure
> fab0c75d x86/cpu: Add platform ID to CPU matching structure
> 7989c393 x86/microcode: Add platform mask to Intel microcode "old" list
>
> The patches fix false-positive "old microcode"/taint-bit-2 reports on Sapphire Rapids and Granite Rapids SKUs.
>
>
>
> [ Test Plan ]
> After booting the system check the /proc/sys/kernel/tainted file for the incorrect microcode error
>
>   Without the fix:
>
>    root at gnh-204:~# cat /proc/sys/kernel/tainted
>    4
>    root at gnh-204:~# dmesg | grep microcode
>    [ 0.000000] x86/CPU: Running old microcode
>    [ 10.088285] microcode: Enabled staging feature.
>    [ 10.092931] microcode: Current revision: 0x01000434
>
>   With the fix:
>
>    root at gnh-204:~# cat /proc/sys/kernel/tainted
>    0
>    root at gnh-204:~# dmesg | grep microcode
>    [ 10.090836] microcode: Enabled staging feature.
>    [ 10.095475] microcode: Current revision: 0x01000434
>
> [ Where problems could occur ]
>
> The regression risk is low. This code is only touching the x86 microcode/CPU-matching code path and no other subsystems are affected.
>
> [ Other Info ]
>
> https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/resolute/+ref/kernel_taint_lp_2161748_intel
>
> Dave Hansen (4):
>    x86/microcode: Refactor platform ID enumeration into a helper
>    x86/cpu: Add platform ID to CPU info structure
>    x86/cpu: Add platform ID to CPU matching structure
>    x86/microcode: Add platform mask to Intel microcode "old" list
>
>   arch/x86/include/asm/microcode.h              |   2 +
>   arch/x86/include/asm/processor.h              |   5 +
>   arch/x86/kernel/cpu/intel.c                   |   1 +
>   arch/x86/kernel/cpu/match.c                   |   3 +
>   .../kernel/cpu/microcode/intel-ucode-defs.h   | 398 +++++++++++-------
>   arch/x86/kernel/cpu/microcode/intel.c         |  54 ++-
>   include/linux/mod_devicetable.h               |   2 +
>   7 files changed, 294 insertions(+), 171 deletions(-)
>
Rejected for the following reasons:
- Missing fix commit for d8630b67ca1e ("x86/cpu: Add platform ID to CPU 
info structure"):
     cda64169bade ("x86/microcode: Do not access MSR_IA32_PLATFORM_ID 
when running as a guest")

- Missing Buglink

Rickey Castillo