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    SubjectRe: [RFC PATCH for 4.18 12/23] cpu_opv: Provide cpu_opv system call (v7)
    On Thu, Apr 12, 2018 at 12:59 PM, Mathieu Desnoyers
    <mathieu.desnoyers@efficios.com> wrote:
    >
    > What are your concerns about page pinning ?

    Pretty much everything.

    It's the most complex part by far, and the vmalloc space is a limited
    resource on 32-bit architectures.

    > Do you have an alternative approach in mind ?

    Do everything in user space.

    And even if you absolutely want cpu_opv at all, why not do it in the
    user space *mapping* without the aliasing into kernel space?

    The cpu_opv approach isn't even fast. It's *really* slow if it has to
    do VM crap.

    The whole rseq thing was billed as "faster than atomics". I
    *guarantee* that the cpu_opv's aren't faster than atomics.

    Linus

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