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

[Alexander Graf <agraf@suse.de>]

On 05/17/2015 01:28 AM, 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>

Sounds plausible to me, though I'm surprised I didn't run into this 
myself yet.

Richard?


Alex

> ---
>   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);