CVS commit: src/sys/arch/x86/x86

["Andrius Varanavicius" <andvar%netbsd.org@localhost>]

Module Name:    src
Committed By:   andvar
Date:           Tue Aug 25 21:06:50 UTC 2026

Modified Files:
        src/sys/arch/x86/x86: identcpu.c

Log Message:
Decode L2 cache associativity for VIA CPUs using the AMD cache lookup table for
the 0x80000006 CPUID function associativity value.

Use `cpuid leaf 4' to get cache parameters for Zhaoxin and late VIA CPU models.

VIA datasheets mention that associativity is stored as a decimal value. However,
in practice, it is encoded the AMD way and does not store the actual value.
Using the raw value leads to an incorrect CPU colors calculation, causing a
panic on KX-7000 (since the result is not a power of two) and incorrect CPU
colors values on other CPU models (e.g. as visible in `vmstat -s').
Decoding value using the AMD cache lookup table produces correct values in all
cases I have tested or verified using CPUID dumps available online.

Additionally, Zhaoxin and late VIA CPUs (CNQ and newer) prefer the Intel
`cpuid leaf 4' function to get cache parameters. Check whether cpuid_level
is equal to or greater than 4 to identify these CPUs and override cache values
(including L1) by calling cpu_dcp_cacheinfo(ci, 4). L3 cache information is
available only through this method.

Fixes PR kern/60619

Similar changes will be committed separately to the cpuctl utility.

pullups to netbsd-11 and netbsd-10 are needed.

Thanks to skrll@ for comments on the patch.


To generate a diff of this commit:
cvs rdiff -u -r1.141 -r1.142 src/sys/arch/x86/x86/identcpu.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.