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    SubjectRe: [PATCH 05/11] x86/fpu: set PKRU state for kernel threads
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    On 10/04/2018 07:05 AM, Sebastian Andrzej Siewior wrote:
    > The PKRU value is not set for kernel threads because they do not have
    > the ->initialized value set. As a result the kernel thread has a random
    > PKRU value set which it inherits from the previous task.
    > It has been suggested by Paolo Bonzini to set it for kernel threads, too
    > because it might be a fix.
    > I *think* this is not required because the kernel threads don't copy
    > data to/from userland and don't have access to any userspace mm in
    > general.
    > However there is this use_mm(). If we gain a mm by use_mm() we don't
    > have a matching PKRU value because those are per thread. It has been
    > suggested to use 0 as the PKRU value but this would bypass PKRU.
    >
    > Set the initial (default) PKRU value for kernel threads.

    We might want to do this for cleanliness reasons... Maybe.

    But this *should* have no practical effects. Kernel threads have no
    real 'mm' and no user pages. They should not have do access to user
    mappings. Protection keys *only* apply to user mappings. Thus,
    logically, they should never be affected by PKRU values.

    So I'm kinda missing the point of the patch.

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