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    SubjectRe: FOR REVIEW: New x86-64 vsyscall vgetcpu()
    Andi Kleen wrote:

    > That is not how user space TLS works. It usually has a base a register.

    Can you please give me a real life (simplified) example?

    > This means it cannot be cache colored (because you would need a static
    > offset) and you couldn't share task_structs on a page.

    I do not see the problem. Can you explain please?
    E.g. the scheduler pulls a task instead of the current one. The CPU
    will see "current->thread_info.cpu"-s of all the tasks at the same
    offset anyway.

    > Also you would make task_struct part of the userland ABI which
    > seems like a very very bad idea to me. It means we couldn't change
    > it anymore.

    We can make some wrapper, e.g.:

    user_per_cpu_var(name, offset)

    "vgetcpu()" would also be added to the ABI which we couldn't change
    easily either.

    Thanks,

    Zoltan
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