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Re: [Qemu-devel] [PATCH] target-s390x: fix CC computation for EX instruc
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH] target-s390x: fix CC computation for EX instruction |
Date: |
Mon, 18 May 2015 08:35:56 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
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 <address@hidden>
> Cc: Alexander Graf <address@hidden>
> Signed-off-by: Aurelien Jarno <address@hidden>
> ---
> 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.
r~