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

From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH] target-s390x: fix CC computation for EX instruction
Date: Mon, 18 May 2015 19:07:21 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

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 <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_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

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


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