Re: [Xen-devel] [PATCH 3/3] xen/arm: set the system time in Xen via the XENPF_settime hypercall

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 5 Nov 2015, Arnd Bergmann wrote:
> On Thursday 05 November 2015 17:09:45 Stefano Stabellini wrote:
> > If Linux is running as dom0, call XENPF_settime to update the system
> > time in Xen on pvclock_gtod notifications.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > ---
> >  arch/arm/xen/enlighten.c |   52 
> > +++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 51 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index b6aea9c..0176db0 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -28,6 +28,7 @@
> >  #include <linux/cpufreq.h>
> >  #include <linux/cpu.h>
> >  #include <linux/console.h>
> > +#include <linux/pvclock_gtod.h>
> >  #include <linux/timekeeping.h>
> >  #include <clocksource/arm_arch_timer.h>
> >  
> > @@ -123,6 +124,50 @@ static void xen_read_wallclock(struct timespec *ts)
> >     set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
> >  }
> >  
> > +static int xen_pvclock_gtod_notify(struct notifier_block *nb,
> > +                              unsigned long was_set, void *priv)
> > +{
> > +   /* Protected by the calling core code serialization */
> > +   static struct timespec next_sync;
> > +
> > +   struct xen_platform_op op;
> > +   struct timespec now;
> 
> Again, use timespec64

OK


> > +   now = __current_kernel_time();
> 
> We don't have __current_kernel_time64() yet, but it is trivial
> to add, just follow the example of
> current_kernel_time()/current_kernel_time64() and convert the
> existing __current_kernel_time() function into a static
> inline wrapper for the new __current_kernel_time64().

All right. I guess something like:

struct timespec64 __current_kernel_time64(void)
{
        struct timekeeper *tk = &tk_core.timekeeper;

        return tk_xtime(tk);
}


> > +   /*
> > +    * We only take the expensive HV call when the clock was set
> > +    * or when the 11 minutes RTC synchronization time elapsed.
> > +    */
> > +   if (!was_set && timespec_compare(&now, &next_sync) < 0)
> > +           return NOTIFY_OK;
> > +
> > +   op.interface_version = XENPF_INTERFACE_VERSION;
> > +   op.cmd = XENPF_settime;
> > +   op.u.settime.secs = now.tv_sec;
> > +   op.u.settime.nsecs = now.tv_nsec;
> > +   op.u.settime.system_time = arch_timer_read_counter();
> > +   printk("GTOD: Setting to %ld.%ld at %lld\n",
> > +          (long)op.u.settime.secs,
> > +          (long)op.u.settime.nsecs,
> > +          (long long)op.u.settime.system_time);
> > +   (void)HYPERVISOR_dom0_op(&op);
> 
> I guess we will also need a XENPF_settime64 interface, but at
> least we can get away with implementing only that one on ARM,
> while x86 will have to support both the 32-bit and 64-bit
> based variant.

We already have XENPF_settime64, I'll just use it instead.

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