amd64/186061: FreeBSD 10 crashes as KVM guest on GNU/Linux on AMD family 10h CPUs

[John Baldwin]

On Wednesday, February 12, 2014 2:40:01 am Simon Matter wrote:
> The following reply was made to PR amd64/186061; it has been noted by GNATS.
> 
> From: "Simon Matter" <simon.matter at invoca.ch>
> To: bug-followup at FreeBSD.org
> Cc: simon.matter at invoca.ch
> Subject: Re: amd64/186061: FreeBSD 10 crashes as KVM guest on GNU/Linux on
>  AMD family 10h CPUs
> Date: Wed, 12 Feb 2014 08:30:51 +0100
> 
>  ------=_20140212083051_97180
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>  
>  As noted by John Baldwin the change to mca.c is not needed. Attached patch
>  is what I'm using now with success.
>  
>  BTW: setting vm.pmap.pg_ps_enabled="0" in loader.conf does also mitigate
>  the issue but I guess it's not the optimal solution.

Talking with Alan Cox, we do think the right fix is to change the test to 
enable the workaround.  However, we'd rather not penalize VM's on other
CPUs.  What we would like to do instead is figure out a set of feature flags
we can test that will assure us we are not on an AMD 10h CPU (e.g. features
that are known to be Intel only, or are known to be on newer AMD CPUs).
However, we haven't come up with that list yet.  Assuming you do have 10h
CPUs, it would be nice to see what cpuid flags are set for your processors.

-- 
John Baldwin