Re: [Qemu-devel] [qemu-s390x] [PATCH for-4.0 2/2] target/s390x: Implement STCK et al for CONFIG_USER_ONLY

[Thomas Huth <thuth@redhat.com>]

On 2018-12-03 15:29, Richard Henderson wrote:
> On 12/3/18 8:02 AM, Thomas Huth wrote:
>> On 2018-12-03 14:27, Richard Henderson wrote:
>>> On 12/3/18 12:19 AM, Thomas Huth wrote:
>>>> On 2018-11-30 20:22, Richard Henderson wrote:
>>>>> This is a non-privileged instruction that was only implemented
>>>>> for system mode.  However, the stck instruction is used by glibc,
>>>>> so this was causing SIGILL for programs run under debian stretch.
>>>>>
>>>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>>>> ---
>>>>>  target/s390x/helper.h      |  2 +-
>>>>>  target/s390x/misc_helper.c | 13 ++++++++++++-
>>>>>  target/s390x/translate.c   |  2 ++
>>>>>  target/s390x/insn-data.def | 11 ++++++-----
>>>>>  4 files changed, 21 insertions(+), 7 deletions(-)
>>>>>
>>>>> diff --git a/target/s390x/helper.h b/target/s390x/helper.h
>>>>> index 018e9dd414..6260b50496 100644
>>>>> --- a/target/s390x/helper.h
>>>>> +++ b/target/s390x/helper.h
>>>>> @@ -121,13 +121,13 @@ DEF_HELPER_4(cu41, i32, env, i32, i32, i32)
>>>>>  DEF_HELPER_4(cu42, i32, env, i32, i32, i32)
>>>>>  DEF_HELPER_5(msa, i32, env, i32, i32, i32, i32)
>>>>>  DEF_HELPER_FLAGS_1(stpt, TCG_CALL_NO_RWG, i64, env)
>>>>> +DEF_HELPER_FLAGS_1(stck, TCG_CALL_NO_RWG_SE, i64, env)
>>>>>  
>>>>>  #ifndef CONFIG_USER_ONLY
>>>>>  DEF_HELPER_3(servc, i32, env, i64, i64)
>>>>>  DEF_HELPER_4(diag, void, env, i32, i32, i32)
>>>>>  DEF_HELPER_3(load_psw, noreturn, env, i64, i64)
>>>>>  DEF_HELPER_FLAGS_2(spx, TCG_CALL_NO_RWG, void, env, i64)
>>>>> -DEF_HELPER_FLAGS_1(stck, TCG_CALL_NO_RWG_SE, i64, env)
>>>>>  DEF_HELPER_FLAGS_2(sck, TCG_CALL_NO_RWG, i32, env, i64)
>>>>>  DEF_HELPER_FLAGS_2(sckc, TCG_CALL_NO_RWG, void, env, i64)
>>>>>  DEF_HELPER_FLAGS_2(sckpf, TCG_CALL_NO_RWG, void, env, i64)
>>>>> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
>>>>> index 3f91579570..c2940afecb 100644
>>>>> --- a/target/s390x/misc_helper.c
>>>>> +++ b/target/s390x/misc_helper.c
>>>>> @@ -76,8 +76,19 @@ uint64_t HELPER(stpt)(CPUS390XState *env)
>>>>>  #endif
>>>>>  }
>>>>>  
>>>>> -#ifndef CONFIG_USER_ONLY
>>>>> +#ifdef CONFIG_USER_ONLY
>>>>> +/* Store Clock */
>>>>> +uint64_t HELPER(stck)(CPUS390XState *env)
>>>>> +{
>>>>> +    struct timespec ts;
>>>>> +    uint64_t ms;
>>>>
>>>> May I suggest "us" for microseconds? "ms" makes me thing of
>>>> "milliseconds"...
>>>
>>> Oops, think-o.
>>>
>>>>> +    clock_gettime(CLOCK_REALTIME, &ts);
>>>>> +    ms = (ts.tv_nsec / 1000) + (ts.tv_sec * 100000ull);
>>>>> +
>>>>> +    return TOD_UNIX_EPOCH + ms;
>>>>> +}
>>>>
>>>> Don't you need to shift the value around a little bit for getting the
>>>> right format of the TOD clock? The microseconds are not starting with
>>>> the lowest bit, the TOD clock has a higher resolution. See also the
>>>> time2tod() macro in include/hw/s390x/tod.h ...
>>>
>>> That's for STCKE, which does use this routine and shift the result around.
>>
>> STCKE certainly has even more bits ... but still, according to the PoP:
>>
>> "The TOD clock nominally is incremented by adding a
>> one in bit position 51 every microsecond."
> 
> I don't see that language within the description of STCK.

It's in chapter 4 instead, the sub-section about "Timing".

 Thomas