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    SubjectRe: [PATCH v9 01/24] mm: Introduce CONFIG_SPECULATIVE_PAGE_FAULT
    On Wed, 28 Mar 2018, Laurent Dufour wrote:

    > >> This configuration variable will be used to build the code needed to
    > >> handle speculative page fault.
    > >>
    > >> By default it is turned off, and activated depending on architecture
    > >> support.
    > >>
    > >> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
    > >> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
    > >> ---
    > >> mm/Kconfig | 3 +++
    > >> 1 file changed, 3 insertions(+)
    > >>
    > >> diff --git a/mm/Kconfig b/mm/Kconfig
    > >> index abefa573bcd8..07c566c88faf 100644
    > >> --- a/mm/Kconfig
    > >> +++ b/mm/Kconfig
    > >> @@ -759,3 +759,6 @@ config GUP_BENCHMARK
    > >> performance of get_user_pages_fast().
    > >>
    > >> See tools/testing/selftests/vm/gup_benchmark.c
    > >> +
    > >> +config SPECULATIVE_PAGE_FAULT
    > >> + bool
    > >
    > > Should this be configurable even if the arch supports it?
    >
    > Actually, this is not configurable unless by manually editing the .config file.
    >
    > I made it this way on the Thomas's request :
    > https://lkml.org/lkml/2018/1/15/969
    >
    > That sounds to be the smarter way to achieve that, isn't it ?
    >

    Putting this in mm/Kconfig is definitely the right way to go about it
    instead of any generic option in arch/*.

    My question, though, was making this configurable by the user:

    config SPECULATIVE_PAGE_FAULT
    bool "Speculative page faults"
    depends on X86_64 || PPC
    default y
    help
    ..

    It's a question about whether we want this always enabled on x86_64 and
    power or whether the user should be able to disable it (right now they
    can't). With a large feature like this, you may want to offer something
    simple (disable CONFIG_SPECULATIVE_PAGE_FAULT) if someone runs into
    regressions.

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