[PATCH 1/3] xen/arm: introduce xen_read_wallclock

[arnd@arndb.de (Arnd Bergmann)]

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@eu.citrix.com>

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