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


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