From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1O6gqi-00026Y-4H
	for qemu-devel@nongnu.org; Tue, 27 Apr 2010 05:13:00 -0400
Received: from [140.186.70.92] (port=50148 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1O6gqg-00025a-AW
	for qemu-devel@nongnu.org; Tue, 27 Apr 2010 05:12:59 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <junkoi2004@gmail.com>) id 1O6gqf-0001By-5a
	for qemu-devel@nongnu.org; Tue, 27 Apr 2010 05:12:58 -0400
Received: from mail-px0-f173.google.com ([209.85.212.173]:56031)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <junkoi2004@gmail.com>) id 1O6gqe-0001BU-T1
	for qemu-devel@nongnu.org; Tue, 27 Apr 2010 05:12:57 -0400
Received: by pxi19 with SMTP id 19so1916134pxi.4
	for <qemu-devel@nongnu.org>; Tue, 27 Apr 2010 02:12:55 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <4BD69C10.50606@siemens.com>
References: <t2yfdaac4d51004252231y2fff0fdne7d8250a21771908@mail.gmail.com>
	<4BD69C10.50606@siemens.com>
From: Jun Koi <junkoi2004@gmail.com>
Date: Tue, 27 Apr 2010 18:12:33 +0900
Message-ID: <p2zfdaac4d51004270212t850d5be1q2fa3447be215209d@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Subject: [Qemu-devel] Re: Problem with watchpoint in gdbstub
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: qemu-devel@nongnu.org

On Tue, Apr 27, 2010 at 5:10 PM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> Jun Koi wrote:
>> Hi,
>>
>> I am trying to debug a VM using gdb. I connected gdb to Qemu (latest
>> code from git repo), and issued below command:
>>
>> ...
>> (gdb) watch *0x77f44cd8
>> (gdb) c
>>
>> The idea is to catch the write access to address 0x77f44cd8.
>>
>> But after the "c" command, I saw that the window title of my VM
>> continuously flip between "QEMU [Stopped]" and "QEMU", non-stop.
>> This makes the VM unusable.
>>
>> Is it a bug? Anybody sees the same problem?
>
> I would bet your watchpoint was established by gdb as a software
> watchpoint. In that case gdb will step through the target, checking
> after each instruction if the memory changed.

But that is certainly not the reason of the symptom I saw.


>
> Is that address valid at the time gdb wants to install it? I saw gdb
> choosing a software watchpoint before when it wasn't.

Yes, that address is valid.

thanks,
J