Re: [qemu-s390x] [PATCH v1 5/7] s390x/tcg: implement SET CLOCK

[David Hildenbrand]

On 04.06.2018 14:05, Cornelia Huck wrote:
> On Fri, 25 May 2018 13:37:06 +0200
> David Hildenbrand <address@hidden> wrote:
> 
>> This allows a guest to change its TOD. We already take care of updating
>> all CKC timers from within S390TODClass.
>>
>> Use MO_ALIGN to load the operand manually - this will properly trigger a
>> SPECIFICATION exception.
>>
>> Signed-off-by: David Hildenbrand <address@hidden>
>> ---
>>  target/s390x/helper.h      |  1 +
>>  target/s390x/insn-data.def |  3 +--
>>  target/s390x/misc_helper.c | 19 +++++++++++++++++++
>>  target/s390x/translate.c   |  9 +++++++++
>>  4 files changed, 30 insertions(+), 2 deletions(-)
>>
> 
>> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
>> index 2ef9de1cca..2f5cd6d22a 100644
>> --- a/target/s390x/misc_helper.c
>> +++ b/target/s390x/misc_helper.c
>> @@ -191,6 +191,25 @@ void tcg_s390_tod_updated(CPUState *cs, run_on_cpu_data 
>> opaque)
>>      helper_sckc(env, env->ckc);
>>  }
>>  
>> +/* Set Clock */
>> +uint32_t HELPER(sck)(CPUS390XState *env, uint64_t tod_low)
>> +{
>> +    S390TODState *td = s390_get_tod();
>> +    S390TODClass *tdc = S390_TOD_GET_CLASS(td);
> 
> Would it make sense to cache the class as well?

Probably, but I don't think this is as critical as the flic (as this
code is TCG only and the class conversion should be fairly fast compared
to a device lookup).

> 
>> +    S390TOD tod = {
>> +        .high = 0,
>> +        .low = tod_low,
>> +    };
>> +    Error *err = NULL;
>> +
>> +    qemu_mutex_lock_iothread();
>> +    tdc->set(td, &tod, &err);
>> +    qemu_mutex_unlock_iothread();
>> +    g_assert(!err);
>> +
>> +    return 0;
>> +}
>> +
> 


-- 

Thanks,

David / dhildenb