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

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Date:   Mon, 7 Aug 2017 20:43:54 +0200
From:   Sebastian Rachuj <rachus@....de>
To:     Paolo Bonzini <pbonzini@...hat.com>, 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

On 07.08.2017 19:50, Paolo Bonzini wrote:
> On 07/08/2017 19:17, Sebastian Rachuj wrote:
>>>>
>>>> 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.
>>
>> Here you are, I hope it helps:
> 
> Not much to say, unfortunately.  It's pretty much the same capabilities
> as a Prescott/Cedar Mill processor, except that it has MSR bitmaps.  It
> also lacks FlexPriority compared to the Conroe I had checked.
> 
> It's not great that even the revert patch doesn't apply cleanly---this
> is *not* necessarily a boring area of the hypervisor...
> 
> Given the rarity of your machine I'm currently leaning towards _not_
> reverting the change.  I'll check another non-Xeon Core 2 tomorrow that
> is from December 2008 (IIRC).  If that one also lacks vNMI, or if I get
> other reports, I suppose I will have to reconsider that.

That's unfortunate to hear. Just for completeness, I want to mention a 
thread in the Archlinux forum, I created, where two other people (Sadar 
and losko) also complained about not working KVM [1]. Additionally, 
Linux 4.12 has not reached yet reached distributions with a greater 
amount of users.

If supporting these chips is too much of a hassle, I will probably have 
to buy a new CPU to enjoy KVM support with a current linux kernel.

Anyway, thanks again for figuring this out!


[1]: https://bbs.archlinux.org/viewtopic.php?id=228645