panic at res.eax == 0

[mmyyrroonn]

Hi, Nice to meet you. Our project met a panic error at the below line. I'm not professional at cpu. May I know in which kind of situation would cause the failure of the following error? Any help would be appreciated.

rust-cpuid/src/lib.rs

Line 271 in 6993bb5

assert!(res.eax == 0);

[gz]

Hi @myronfanqiu

Can you tell me what CPU model this is where you encounter this error? And maybe cpuid --raw if you're running this on Linux. Thanks!

[programmerjake]

Apparently that assert should just be deleted since, according to Wikipedia, eax is set to the highest input ecx value supported for the input eax == 7. In particular, avx512_bf16 is returned from input eax == 7, ecx == 1

https://en.wikipedia.org/wiki/CPUID#EAX=7,_ECX=0:_Extended_Features

[programmerjake]

thread '<unnamed>' panicked at 'assertion failed: res.eax == 0', /root/.cargo/registry/src/github.com-1ecc6299db9ec823/raw-cpuid-7.0.3/src/lib.rs:295:13

running into this issue on a Intel(R) Xeon(R) Gold 6348H:
/proc/cpuinfo: https://pastebin.ubuntu.com/p/g9NkyVjbQG/

it supports avx512_bf16, so must return an eax of at least 1.

[gz]

Hi thanks for reporting this,yea this makes sense I think this sub-leaf is new and the assert was too pessimistic assuming they'll never add one. I'll remove the assert.

[gz]

Released a fixed version as 9.0.1. This doesn't quite allow to query for avx_bf16 yet, I'll update the cpuid library more for that.

[programmerjake]

Thanks!