Re: [Qemu-devel] [PATCH] target-arm: Use common CPU cycle infrastructure

[Paolo Bonzini]

On 06/10/2015 15:06, Peter Maydell wrote:
> Looking closer, clock_gettime() also has a userspace
> only fastpath in the VDSO.

Yup, hence the patch that changed the default cpu_get_real_ticks()
implementation to get_clock().

>> > Could we just use CNTVCT_EL0?  Which cores have it?
>
> Not guaranteed to be enabled for userspace access by the kernel,
> and even if it is enabled, the kernel folks don't (last time I
> checked) consider this userspace ABI -- it's only there for
> the benefit of the VDSO.

Ok, thanks.

> (CNTVCT_EL0 is how the fast clock_gettime
> and getimeofday paths are implemented.)

Yes.

Paolo