Re: [Minios-devel] [UNIKRAFT PATCHv5 24/46] plat/kvm: Introduce a time_ops for different architectures

["Wei Chen (Arm Technology China)" <Wei.Chen@xxxxxxx>]

Hi Simon,

> -----Original Message-----
> From: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> Sent: 2018年9月6日 23:53
> To: Wei Chen (Arm Technology China) <Wei.Chen@xxxxxxx>; minios-
> devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Kaly Xin (Arm Technology China) <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> Subject: Re: [Minios-devel] [UNIKRAFT PATCHv5 24/46] plat/kvm: Introduce a
> time_ops for different architectures
> 
> Hi Wei,
> 
> On 10.08.2018 09:08, Wei Chen wrote:
> > Different architectures have different timer implementation. In
> > order to avoid using too many #ifdef, we introduce this time_ops
> > for different architectures to implement arch_timer_ops.
> 
> does the timer implementation this change during runtime or can you
> settle on one specific timer implementation during compile time?

No, timer implementation is settled during compile time, it could not
be changed during runtime.

> Why not providing a different C file that implements your ARM timer? We
> could avoid the indirection and save the timeops struct.

I have implemented a different C file for ARM timer already. But I can't
use the same API names for ARM timer library. Because the tscclock_ prefix
is x86 specific. If I don't use the arch_timer_ops to standardize the
callback function, in ukplat_monotonic_clock we have to use:

__nsec ukplat_monotonic_clock(void)
{
#if defined(__x86_64__)
return tscclock_monotonic();
#else if defined(__ARM64__)
return generic_timer_monotonic ();
#endif
}

> 
> >
> > Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> > ---
> >   include/uk/plat/time.h | 8 ++++++++
> >   plat/kvm/time.c        | 7 ++++---
> >   plat/kvm/tscclock.c    | 6 ++++++
> >   3 files changed, 18 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/uk/plat/time.h b/include/uk/plat/time.h
> > index 202e0f9..2aacfce 100644
> > --- a/include/uk/plat/time.h
> > +++ b/include/uk/plat/time.h
> > @@ -47,6 +47,14 @@ void ukplat_time_fini(void);
> >
> >   __nsec ukplat_monotonic_clock(void);
> >
> > +struct ukplat_time_ops {
> > +   int (*init)(void);
> > +   __u64 (*monotonic)(void);
> > +   __u64 (*epochoffset)(void);
> > +};
> > +
> > +extern struct ukplat_time_ops arch_timer_ops;
> > +
> >   #ifdef __cplusplus
> >   }
> >   #endif
> > diff --git a/plat/kvm/time.c b/plat/kvm/time.c
> > index 1fb48bf..eb8bfc2 100644
> > --- a/plat/kvm/time.c
> > +++ b/plat/kvm/time.c
> > @@ -31,17 +31,18 @@
> >   #include <kvm/tscclock.h>
> >   #include <uk/assert.h>
> >
> > +struct ukplat_time_ops *time_ops = &arch_timer_ops;
> >
> >   /* return ns since time_init() */
> >   __nsec ukplat_monotonic_clock(void)
> >   {
> > -   return tscclock_monotonic();
> > +   return time_ops->monotonic();
> >   }
> >
> >   /* return wall time in nsecs */
> >   __nsec ukplat_clock_wall(void)
> >   {
> > -   return tscclock_monotonic() + tscclock_epochoffset();
> > +   return time_ops->monotonic() + time_ops->epochoffset();
> >   }
> >
> >   static int timer_handler(void *arg __unused)
> > @@ -59,7 +60,7 @@ void ukplat_time_init(void)
> >     if (rc < 0)
> >             UK_CRASH("Failed to register timer interrupt handler\n");
> >
> > -   rc = tscclock_init();
> > +   rc = time_ops->init();
> >     if (rc < 0)
> >             UK_CRASH("Failed to initialize TSCCLOCK\n");
> >   }
> > diff --git a/plat/kvm/tscclock.c b/plat/kvm/tscclock.c
> > index 8961659..990902b 100644
> > --- a/plat/kvm/tscclock.c
> > +++ b/plat/kvm/tscclock.c
> > @@ -358,3 +358,9 @@ void time_block_until(__snsec until)
> >                     break;
> >     }
> >   }
> > +
> > +struct ukplat_time_ops arch_timer_ops = {
> > +   .init = tscclock_init,
> > +   .monotonic = tscclock_monotonic,
> > +   .epochoffset = tscclock_epochoffset,
> > +};
> >
> 
> Thanks,
> 
> Simon
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