Re: [Xen-devel] [PATCH 1/3] xen/arm: introduce xen_read_wallclock

[Arnd Bergmann <arnd@xxxxxxxx>]

On Thursday 05 November 2015 17:09:43 Stefano Stabellini wrote:
> Read the wallclock from the shared info page at boot time.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

Please use the appropriate timespec64 based functions here,
we are in the process of converting all callers of struct timespec.

> ---
> +static void xen_read_wallclock(struct timespec *ts)
> +{
> +     u32 version;
> +     u64 delta;
> +     struct timespec now;
> +     struct shared_info *s = HYPERVISOR_shared_info;
> +     struct pvclock_wall_clock *wall_clock = &(s->wc);

pvclock_wall_clock has a 'u32 sec', so that suffers from
a potential overflow. We should try to avoid introducing that
on ARM, and instead have a 64-bit seconds based version,
or alternatively a 64-bit nanoseconds version (with no
extra seconds) that is also sufficient.

>       struct vcpu_register_vcpu_info info;
> @@ -218,6 +246,7 @@ static int __init xen_guest_init(void)
>       struct shared_info *shared_info_page = NULL;
>       struct resource res;
>       phys_addr_t grant_frames;
> +     struct timespec ts;
>  
>       if (!xen_domain())
>               return 0;
> @@ -291,6 +320,8 @@ static int __init xen_guest_init(void)
>  
>       pv_time_ops.steal_clock = xen_stolen_accounting;
>       static_key_slow_inc(&paravirt_steal_enabled);
> +     xen_read_wallclock(&ts);
> +     do_settimeofday(&ts);
>  

Once you can get a 64-bit time, call do_settimeofday64()
here.

        Arnd

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