linux-kernel - Re: kvm_intel fails to load on Conroe CPUs running Linux 4.12

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Date:   Mon, 7 Aug 2017 10:12:33 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sebastian Rachuj <rachus@....de>, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: kvm_intel fails to load on Conroe CPUs running Linux 4.12

Paolo Bonzini <pbonzini@...hat.com> wrote:

> On 06/08/2017 23:23, Sebastian Rachuj wrote:
>> On 06.08.2017 23:10, Paolo Bonzini wrote:
>>> On 05/08/2017 21:26, Sebastian Rachuj wrote:
>>>> Dear linux developers,
>>>> 
>>>> since my upgrade from linux 4.11 to linux 4.12 the "kvm_intel" module
>>>> does not load correctly anymore. "Modprobing" the kernel module gives an
>>>> Input/Output error. It seems to be related to the CPU architecture and
>>>> (to my knowledge) affects Conroe CPUs. I did a bisect and found the
>>>> following commit as the guilty one:
>>> 
>>> What is your cpuinfo?  I tested on a Conroe Xeon X3220 (family 6,
>>> model 15, stepping 11) when I posted that patch, and it did have virtual
>>> NMIs.
>> 
>> Thank you for looking into the issue. My cpuinfo is as follows:
> 
> Looks like Intel was already differentiating virtualization features
> across SKUs.  Please run the attached script as root to see what other
> things are different (apparently) between non-Xeon and Xeon Conroes.

There may be another explanation. If I remember correctly from my days in
Intel, Intel initially sold CMWA (Conroe) B-step. The next step, E-step,
introduced a couple of new features, which may have included vNMI.

The CPU of Sebastian appears to be B1 according to cpuinfo.

Nadav