Re: [PATCH 2/2] cpu: intel, amd: mask cleared cpuid features

[Borislav Petkov]

On Tue, Jul 24, 2012 at 11:06:08AM +0400, Vladimir Davydov wrote:
> If msr-tools are used for cpuid masking, we will either get
> inconsistency between /proc/cpuinfo:flags and the output of the cpuid
> instruction or have to "synchronize" the clearcpuid boot option and
> the userspace app using msr-tools, which seems to be inconvenient.

Right, so IMO what you want to do is not very kosher as a generic kernel
feature for reasons described earlier.

And yes, "synchronizing" /proc/cpuinfo's flags and CPUID output is a lot
less pain compared to having a generic abusable feature.

And also much better suited for your niche use case than opening this up
as a generic functionality to the wide public which will most definitely
find productive ways to abuse this.

Simply ask yourself this: is this something which the majority of
x86 linux users will benefit from or is it only something which is
nice-to-have solely for our single use case?

Thanks.

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