Re: [Qemu-devel] [PATCH] target-s390x: fix CC computation for EX instruction

[Alexander Graf <agraf@suse.de>]

On 05/18/2015 05:35 PM, Richard Henderson wrote:
> On 05/16/2015 04:28 PM, Aurelien Jarno wrote:
>> Commit 7a6c7067f optimized CC computation by only saving cc_op before
>> calling helpers as they either don't touch the CC or generate a new
>> static value. This however doesn't work for the EX instruction as the
>> helper changes or not the CC value depending on the actual executed
>> instruction (e.g. MVC vs CLC).
>>
>> This patches force a CC computation before calling the helper. This
>> fixes random memory corruption occuring in guests.
>>
>> Cc: Richard Henderson <rth@twiddle.net>
>> Cc: Alexander Graf <agraf@suse.de>
>> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
>> ---
>>   target-s390x/translate.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/target-s390x/translate.c b/target-s390x/translate.c
>> index 80e3a54..10522df 100644
>> --- a/target-s390x/translate.c
>> +++ b/target-s390x/translate.c
>> @@ -2095,7 +2095,7 @@ static ExitStatus op_ex(DisasContext *s, DisasOps *o)
>>       TCGv_i64 tmp;
>>   
>>       update_psw_addr(s);
>> -    update_cc_op(s);
>> +    gen_op_calc_cc(s);
>>   
>>       tmp = tcg_const_i64(s->next_pc);
>>       gen_helper_ex(cc_op, cpu_env, cc_op, o->in1, o->in2, tmp);
> I agree this is a bug, and the right fix.
>
> You can also remove the set_cc_static at the end of op_ex, since that's done by
> gen_op_calc_cc.

Thanks, I applied the patch and did the change to remove set_cc_static 
from op_ex locally.


Alex