Re: [Qemu-devel] [qemu-s390x] [PATCH v3 5/9] s390x/tcg: properly implement the TOD

[David Hildenbrand <david@redhat.com>]

On 26.06.2018 14:27, Cornelia Huck wrote:
> On Tue, 26 Jun 2018 14:06:00 +0200
> David Hildenbrand <david@redhat.com> wrote:
> 
>>>> @@ -34,10 +58,24 @@ static void qemu_s390_tod_class_init(ObjectClass *oc, void *data)
>>>>      tdc->set = qemu_s390_tod_set;
>>>>  }
>>>>  
>>>> +static void qemu_s390_tod_init(Object *obj)
>>>> +{
>>>> +    S390TODState *td = S390_TOD(obj);
>>>> +    struct tm tm;
>>>> +
>>>> +    qemu_get_timedate(&tm, 0);
>>>> +    td->base.high = 0;
>>>> +    td->base.low = TOD_UNIX_EPOCH + (time2tod(mktimegm(&tm)) * 1000000000ULL);
>>>> +    if (td->base.low < TOD_UNIX_EPOCH) {
>>>> +        td->base.high += 1;
>>>> +    }
>>>> +}  
>>>
>>> Nit: It would be sufficient to do this in the realize() function instead.  
>>
>> Then I'll have to overwrite the realize function and store the
>> parent_realize function - something that I want to avoid if not really
>> necessary.
> 
> Agreed. I'd just leave it as it is now.
> 
>>
>> (for now it was also done in the cpu initfn, so that should be fine)
>>
>>>   
>>>>  static TypeInfo qemu_s390_tod_info = {
>>>>      .name = TYPE_QEMU_S390_TOD,
>>>>      .parent = TYPE_S390_TOD,
>>>>      .instance_size = sizeof(S390TODState),
>>>> +    .instance_init = qemu_s390_tod_init,
>>>>      .class_init = qemu_s390_tod_class_init,
>>>>      .class_size = sizeof(S390TODClass),
>>>>  };  
>>> [...]  
>>>> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
>>>> index dd5273949b..be341b5295 100644
>>>> --- a/target/s390x/misc_helper.c
>>>> +++ b/target/s390x/misc_helper.c
>>>> @@ -28,6 +28,8 @@
>>>>  #include "qemu/timer.h"
>>>>  #include "exec/exec-all.h"
>>>>  #include "exec/cpu_ldst.h"
>>>> +#include "qapi/error.h"
>>>> +#include "tcg_s390x.h"
>>>>  
>>>>  #if !defined(CONFIG_USER_ONLY)
>>>>  #include "sysemu/cpus.h"
>>>> @@ -39,6 +41,7 @@
>>>>  #include "hw/s390x/ioinst.h"
>>>>  #include "hw/s390x/s390-pci-inst.h"
>>>>  #include "hw/boards.h"
>>>> +#include "hw/s390x/tod.h"
>>>>  #endif
>>>>  
>>>>  /* #define DEBUG_HELPER */
>>>> @@ -138,25 +141,32 @@ void HELPER(spx)(CPUS390XState *env, uint64_t a1)
>>>>  /* Store Clock */
>>>>  uint64_t HELPER(stck)(CPUS390XState *env)
>>>>  {
>>>> -    uint64_t time;
>>>> +    S390TODState *td = s390_get_todstate();
>>>> +    S390TODClass *tdc = S390_TOD_GET_CLASS(td);
>>>> +    S390TOD tod;
>>>>  
>>>> -    time = env->tod_offset +
>>>> -        time2tod(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
>>>> -
>>>> -    return time;
>>>> +    tdc->get(td, &tod, &error_abort);
>>>> +    return tod.low;
>>>>  }
>>>>  
>>>>  /* Set Clock Comparator */
>>>>  void HELPER(sckc)(CPUS390XState *env, uint64_t time)
>>>>  {
>>>> +    S390TODState *td = s390_get_todstate();
>>>> +    S390TODClass *tdc = S390_TOD_GET_CLASS(td);
>>>> +    S390TOD tod_base;
>>>> +
>>>>      if (time == -1ULL) {
>>>>          return;
>>>>      }
>>>>  
>>>>      env->ckc = time;
>>>>  
>>>> +    tdc->get(td, &tod_base, &error_abort);
>>>> +    tod_base.low -= time2tod(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));  
>>>
>>> So the tdc->get first adds the time2tod, and then you subtract it here
>>> again? Can't you simply use td->base.low directly instead?  
>>
>> That might be a good idea, previously I had tdc->get_base(), but dropped
>> it because it cannot be implemented for KVM.
>>
>> Simply accessing the member here should be fine. Thanks!
> 
> So, we're guaranteed to have td->base.low at the correct value? (Sorry,
> having a bit of a hard time following around here.)
> 

Yes, just verified, changed and tested. We will have the value at that
place.

I'll give some more time to review the other parts, then I can resend.


-- 

Thanks,

David / dhildenb