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Subject: Re: CPU microcode reported wrong in /proc/cpuinfo
To: cygwin@cygwin.com
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From: Brian Inglis <Brian.Inglis@SystematicSw.ab.ca>
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Message-ID: <68eea787-9cde-d6ed-499b-61dfc036adff@SystematicSw.ab.ca>
Date: Thu, 9 Jul 2020 19:27:29 -0600
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Cc: "Lavrentiev, Anton \(NIH/NLM/NCBI\) \[C\]" <lavr@ncbi.nlm.nih.gov>
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On 2020-06-10 15:45, Brian Inglis wrote:
> On 2020-06-10 14:23, Lavrentiev, Anton (NIH/NLM/NCBI) [C] via Cygwin wrote:
>>> I'll have to recheck how Linux handles these
>>
>> JFYI I was in correspondence with the cpuid utility team lately, and they told me that Linux uses vendor-specific MSRs to pull that info out:
>>
>>> Check out:
>>>
>>>    MSR_IA32_UCODE_REV
>>>    MSR_AMD64_PATCH_LEVEL
>>>
>>> Both reference MSR 0x8b.
> 
> As does MS, as I also tracked down some older MS Windows microcode registry
> values used, whose names also appear to be based on the earlier MSR names.
> Using MSRs are not an option, as MS Windows appears to provide no documented
> access to those register values, and they are only accessible from kernel level
> drivers, which are not available for latest MS Windows (i.e. I don't trust
> offered drivers that claim to provide MSR access!)
> 
> I have applied a patch for this, and rebuilt cygwin, but are having problems
> testing with the new dll (as are some others), so need some time to figure out
> what are the minimum synced pieces now required to be able to test!

Managed to get this tested and applied thanks to your help and it has landed in
new Cygwin 3.1.6 so please post your results and any further comments when you
have a chance to upgrade and test.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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