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    SubjectRe: [PATCH] kcsan: use u64 instead of cycles_t
    +Cc: Paul

    On Thu, 29 Jul 2021 at 16:28, Heiko Carstens <hca@linux.ibm.com> wrote:
    >
    > cycles_t has a different type across architectures: unsigned int,
    > unsinged long, or unsigned long long. Depending on architecture this
    > will generate this warning:
    >
    > kernel/kcsan/debugfs.c: In function ‘microbenchmark’:
    > ./include/linux/kern_levels.h:5:25: warning: format ‘%llu’ expects argument of type ‘long long unsigned int’, but argument 3 has type ‘cycles_t’ {aka ‘long unsigned int’} [-Wformat=]
    >
    > To avoid this simple change the type of cycle to u64 in
    > microbenchmark(), since u64 is of type unsigned long long for all
    > architectures.
    >
    > Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

    Acked-by: Marco Elver <elver@google.com>

    Do you have a series adding KCSAN support for s390, i.e. would you
    like to keep it together with those changes?

    Otherwise this would go the usual route through Paul's -rcu tree.

    Thanks,
    -- Marco

    > ---
    > kernel/kcsan/debugfs.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
    > index e65de172ccf7..1d1d1b0e4248 100644
    > --- a/kernel/kcsan/debugfs.c
    > +++ b/kernel/kcsan/debugfs.c
    > @@ -64,7 +64,7 @@ static noinline void microbenchmark(unsigned long iters)
    > {
    > const struct kcsan_ctx ctx_save = current->kcsan_ctx;
    > const bool was_enabled = READ_ONCE(kcsan_enabled);
    > - cycles_t cycles;
    > + u64 cycles;
    >
    > /* We may have been called from an atomic region; reset context. */
    > memset(&current->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
    > --
    > 2.25.1
    >
    > --
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