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

[Vladimir Davydov <vdavydov@parallels.com>]

On 07/25/2012 02:43 PM, Borislav Petkov wrote:
> On Wed, Jul 25, 2012 at 02:31:23PM +0400, Vladimir Davydov wrote:
>> So, you prefer adding some filtering of /proc/cpuinfo into the
>> mainstream kernel
> That's already there right? And your 1/2 patch was making toggling those
> bits easier.
>
>> (not now, later, for LXC to work) instead of enabling clearcpuid boot
>> option to mask CPUID features? IMO, the latter would look clearer.
> Yes, but for reasons noted earlier, you cannot tweak all hardware CPUID
> features as you want them.
>
> So, having a software-only layer of tweaking /proc/cpuinfo or something
> different you can come up with is the only option you have.
>
> And even in that case, applications running in the container which
> execute CPUID might fail in a strange manner when the corresponding
> /proc/cpuinfo flag was cleared by you intentionally but the hardware
> CPUID flag is there. In such situations, issues like that should
> probably be sorted on a case-by-case basis I guess.
>
> Thanks.
>

We've agreed that tweaking CPUID bits in kernel is not a good idea and 
it is better to think about virtualization of /proc/cpuinfo and using 
msr-tools.

Thank you for your time and feedback.