From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:43251)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <smolov@ispras.ru>) id 1ZygzG-00065h-E3
	for qemu-devel@nongnu.org; Tue, 17 Nov 2015 09:11:59 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <smolov@ispras.ru>) id 1ZygzC-0005dZ-AY
	for qemu-devel@nongnu.org; Tue, 17 Nov 2015 09:11:58 -0500
Received: from smtp.ispras.ru ([83.149.199.79]:50964)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <smolov@ispras.ru>) id 1ZygzC-0005d6-3Q
	for qemu-devel@nongnu.org; Tue, 17 Nov 2015 09:11:54 -0500
References: <5638B3E4.8020906@ispras.ru>
	<CAFEAcA_O28TP-LZ584yy_EpHMeK9Y6cKOigXHC1_bkP3AauoxQ@mail.gmail.com>
	<CAPokK=pct3g5QEoWR9h=tbjTA+7j6HFKwqUWLwVGrLbMbH4XkA@mail.gmail.com>
From: Sergey Smolov <smolov@ispras.ru>
Message-ID: <564B27CB.7010302@ispras.ru>
Date: Tue, 17 Nov 2015 17:12:43 +0400
MIME-Version: 1.0
In-Reply-To: <CAPokK=pct3g5QEoWR9h=tbjTA+7j6HFKwqUWLwVGrLbMbH4XkA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: quoted-printable
Subject: Re: [Qemu-devel] log every write to register
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: Peter Crosthwaite <crosthwaitepeter@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, Richard Henderson <rth@twiddle.net>
Cc: QEMU Developers <qemu-devel@nongnu.org>


03.11.2015 20:29, Peter Crosthwaite =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> On Tue, Nov 3, 2015 at 8:14 AM, Peter Maydell <peter.maydell@linaro.org=
> wrote:
>> On 3 November 2015 at 13:17, Sergey Smolov <smolov@ispras.ru> wrote:
>>> I have a collection of ARMv8 register names. I need to add special lo=
gging
>>> mode to QEMU so that every time it is enabled, every write access to =
any of
>>> the specified registers will produce a new record to log, including r=
egister
>>> name and a value to be written.
>>>
>>> Is it possible to accomplish such a task? If yes, where shall I find
>>> functions that implement "writing to register" functionality?
>> This is difficult, because we don't have a single convenient
>> location which all register accesses go through. (General purpose
>> registers and some system registers will be optimised so that
>> accesses are made directly from JIT generated code.)
>>
> You may be able to hack the TCG generation functions to call out to
> helper context (which implements your log) on each op that updates
> your specific regs. It will kill performance though if those registers
> are hot.

Thank you for your answer!
Could you explain the idea in a more detailed way?
Which TCG generation functions should i hack for write-to-specific-regs=20
logging?

Thanks in advance,
Sergey Smolov