Re: [PATCH v3 14/18] target/s390x: Rely on unwinding in s390_cpu_tlb_fill

[Richard Henderson]

On 9/27/19 4:02 AM, David Hildenbrand wrote:
> On 26.09.19 18:26, Richard Henderson wrote:
>> We currently set ilen to AUTO, then overwrite that during
>> unwinding, then overwrite that for the code access case.
>>
>> This can be simplified to setting ilen to our arbitrary
>> value for the (undefined) code access case, then rely on
>> unwinding to overwrite that with the correct value for
>> the data access case.
>>
>> Signed-off-by: Richard Henderson <address@hidden>
>> ---
>>  target/s390x/excp_helper.c | 23 +++++++----------------
>>  1 file changed, 7 insertions(+), 16 deletions(-)
>>
>> diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c
>> index 98a1ee8317..8ce992e639 100644
>> --- a/target/s390x/excp_helper.c
>> +++ b/target/s390x/excp_helper.c
>> @@ -96,7 +96,7 @@ bool s390_cpu_tlb_fill(CPUState *cs, vaddr address, int 
>> size,
>>  {
>>      S390CPU *cpu = S390_CPU(cs);
>>  
>> -    trigger_pgm_exception(&cpu->env, PGM_ADDRESSING, ILEN_AUTO);
>> +    trigger_pgm_exception(&cpu->env, PGM_ADDRESSING, ILEN_UNWIND);
> 
> Hmm, we always trigger a pgm exceptions, meaning we set
> cs->exception_index even if we have probe = true. Confused by that.

This is the CONFIG_USER_ONLY version, for which probe is always false.  Perhaps
I shouldn't have made the function interface identical, but it did appear to
make things cleaner for most targets.

>> +    trigger_pgm_exception(env, excp, 2);
> 
> I wonder if it is still worth setting this only conditionally. Most
> probably not.

I don't see that it would be.  I hope the comment is clear about this arbitrary
value is overwritten during unwinding.


r~