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SubjectRe: [PATCH v3 2/6] perf tsc: Add rdtsc() for Arm64
On Wed, Sep 02, 2020 at 02:21:27PM +0100, Leo Yan wrote:
> The system register CNTVCT_EL0 can be used to retrieve the counter from
> user space. Add rdtsc() for Arm64.

> +u64 rdtsc(void)
> +{
> + u64 val;

Would it make sense to put a comment in that this counter is/could-be
'short' ? Because unlike x86-TSC, this thing isn't architecturally
specified to be 64bits wide.

> + asm volatile("mrs %0, cntvct_el0" : "=r" (val));
> +
> + return val;
> +}
> --
> 2.17.1
>

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