From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1JASSF-0003Tv-PT
	for qemu-devel@nongnu.org; Thu, 03 Jan 2008 10:57:59 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1JASSE-0003RH-01
	for qemu-devel@nongnu.org; Thu, 03 Jan 2008 10:57:59 -0500
Received: from [199.232.76.173] (helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1JASSD-0003Qw-NR
	for qemu-devel@nongnu.org; Thu, 03 Jan 2008 10:57:57 -0500
Received: from nf-out-0910.google.com ([64.233.182.186])
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <blauwirbel@gmail.com>) id 1JASSD-0001oJ-8a
	for qemu-devel@nongnu.org; Thu, 03 Jan 2008 10:57:57 -0500
Received: by nf-out-0910.google.com with SMTP id 30so435295nfu.12
	for <qemu-devel@nongnu.org>; Thu, 03 Jan 2008 07:57:56 -0800 (PST)
Message-ID: <f43fc5580801030757q1428a13cu6be9d74f7d911dde@mail.gmail.com>
Date: Thu, 3 Jan 2008 17:57:55 +0200
From: "Blue Swirl" <blauwirbel@gmail.com>
Subject: Re: [Qemu-devel] qemu cpu-all.h exec.c
In-Reply-To: <200801030118.59970.paul@codesourcery.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
References: <E1J9kQZ-0006Tj-Gh@cvs.savannah.gnu.org>
	<200801021718.06316.paul@codesourcery.com>
	<f43fc5580801020931v6166c8a2q2d6526bec4e91e73@mail.gmail.com>
	<200801030118.59970.paul@codesourcery.com>
Reply-To: qemu-devel@nongnu.org
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: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org

On 1/3/08, Paul Brook <paul@codesourcery.com> wrote:
> On Wednesday 02 January 2008, Blue Swirl wrote:
> > On 1/2/08, Paul Brook <paul@codesourcery.com> wrote:
> > > > Also the opaque parameter may need to be different for each function,
> > > > it just didn't matter for the unassigned memory case.
> > >
> > > Do you really have systems where independent devices need to respond to
> > > different sized accesses to the same address?
> >
> > I don't think so. But one day unassigned or even normal RAM memory
> > access may need an opaque parameter, so passing the device's opaque to
> > unassigned memory handler is wrong.
>
> I'm not convinced.  Your current implementation seems to introduce an extra
> level of indirection without any plausible benefit.
>
> If you're treating unassigned memory differently it needs to be handled much
> earlier that so you can raise CPU exceptions.

Earlier, where's that?

Another approach could be conditional stacked handlers, where a higher
level handler could pass the access request to lower one (possibly
modifying it in flight) or handle completely. Maybe this solves the
longstanding generic DMA issue if taken to the device to memory
direction.