From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:41980)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1agcAs-0000oy-GA
	for qemu-devel@nongnu.org; Thu, 17 Mar 2016 13:57:36 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1agcAo-00089F-Fq
	for qemu-devel@nongnu.org; Thu, 17 Mar 2016 13:57:30 -0400
Received: from mail-qk0-x244.google.com ([2607:f8b0:400d:c09::244]:34967)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1agcAo-00088z-AU
	for qemu-devel@nongnu.org; Thu, 17 Mar 2016 13:57:26 -0400
Received: by mail-qk0-x244.google.com with SMTP id s5so2775228qkd.2
	for <qemu-devel@nongnu.org>; Thu, 17 Mar 2016 10:57:25 -0700 (PDT)
Sender: Richard Henderson <rth7680@gmail.com>
References: <1458222382-6498-1-git-send-email-sergey.fedorov@linaro.org>
	<1458222382-6498-4-git-send-email-sergey.fedorov@linaro.org>
From: Richard Henderson <rth@twiddle.net>
Message-ID: <56EAF001.2050303@twiddle.net>
Date: Thu, 17 Mar 2016 10:57:21 -0700
MIME-Version: 1.0
In-Reply-To: <1458222382-6498-4-git-send-email-sergey.fedorov@linaro.org>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH 3/5] tcg: always keep jump target and
 tb->jmp_next consistent
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: sergey.fedorov@linaro.org, qemu-devel@nongnu.org
Cc: Sergey Fedorov <serge.fdrv@gmail.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>

On 03/17/2016 06:46 AM, sergey.fedorov@linaro.org wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> Simple code simplification.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
> ---
>  translate-all.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/translate-all.c b/translate-all.c
> index f17ace1ae899..a1ac9841de48 100644
> --- a/translate-all.c
> +++ b/translate-all.c
> @@ -927,6 +927,14 @@ static inline void tb_page_remove(TranslationBlock **ptb, TranslationBlock *tb)
>      }
>  }
>  
> +/* reset the jump entry 'n' of a TB so that it is not chained to
> +   another TB */
> +static inline void tb_reset_jump(TranslationBlock *tb, int n)
> +{
> +    tb_set_jmp_target(tb, n, (uintptr_t)(tb->tc_ptr + tb->tb_next_offset[n]));
> +    tb->jmp_next[n] = NULL;
> +}
> +
>  static inline void tb_jmp_remove(TranslationBlock *tb, int n)
>  {
>      TranslationBlock *tb1, **ptb;
> @@ -951,18 +959,10 @@ static inline void tb_jmp_remove(TranslationBlock *tb, int n)
>          }
>          /* now we can suppress tb(n) from the list */
>          *ptb = tb->jmp_next[n];
> -
> -        tb->jmp_next[n] = NULL;
> +        tb_reset_jump(tb, n);

What's the motivation here?  This implies an extra cache flush.
Where were we resetting the jump previously?  Or is this a bug
in that we *weren't* resetting the jump previously?


r~