From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=39432 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1OqRQi-0001qW-5i
	for qemu-devel@nongnu.org; Tue, 31 Aug 2010 10:03:19 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <anthony@codemonkey.ws>) id 1OqRLn-0004tx-8Q
	for qemu-devel@nongnu.org; Tue, 31 Aug 2010 09:58:16 -0400
Received: from mail-vw0-f45.google.com ([209.85.212.45]:62147)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <anthony@codemonkey.ws>) id 1OqRLn-0004tm-3H
	for qemu-devel@nongnu.org; Tue, 31 Aug 2010 09:58:11 -0400
Received: by vws19 with SMTP id 19so5591409vws.4
	for <qemu-devel@nongnu.org>; Tue, 31 Aug 2010 06:58:10 -0700 (PDT)
Message-ID: <4C7D0A6E.8000302@codemonkey.ws>
Date: Tue, 31 Aug 2010 08:58:06 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] Re: [PATCH 5/5] RFC: distinguish warm reset from
	cold reset.
References: <cover.1283152674.git.yamahata@valinux.co.jp>
	<0a460e01cca4fa24f446c7a715fe6df17d0be9ed.1283152674.git.yamahata@valinux.co.jp>
	<4C7BAB2A.30608@codemonkey.ws>
	<20100831025808.GA19374@valinux.co.jp>
	<4C7CFEC1.8040204@codemonkey.ws>
	<20100831131449.GG10499@redhat.com>
	<4C7D01B3.4030602@codemonkey.ws>
	<20100831132158.GH10499@redhat.com>
	<4C7D02FB.4030706@codemonkey.ws> <4C7D03C7.9090406@redhat.com>
	<4C7D04E4.2060305@codemonkey.ws> <4C7D07B9.4090909@redhat.com>
In-Reply-To: <4C7D07B9.4090909@redhat.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
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.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: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Avi Kivity <avi@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>, glommer@redhat.com, qemu-devel@nongnu.org, blauwirbel@gmail.com, Isaku Yamahata <yamahata@valinux.co.jp>, alex.williamson@redhat.com

On 08/31/2010 08:46 AM, Avi Kivity wrote:
>  On 08/31/2010 04:34 PM, Anthony Liguori wrote:
>> On 08/31/2010 08:29 AM, Avi Kivity wrote:
>>> Note, for most devices there's no difference.  x86 has INIT and 
>>> RESET, with the keyboard controller RESET signal sometimes wired to 
>>> INIT, and RAM doesn't have RESET.  Otherwise most devices don't see 
>>> a difference.
>>
>> Yes, that's why I'm wondering if we can just get away with using a 
>> simple reset() callback and for the handful of devices that don't do 
>> a full reset, they can just move the state unaffected by warm reset 
>> to ->init().
>>
>
> This seems reasonable.

But I'm still not sure whether the reset signal can be deliver based on 
a pre-order transversal or whether a custom transversal was required 
that each bus participates in.

>> For cold reset, I'd rather approach it as a device destroy + create.  
>> This means that given a DeviceState, we need to collect enough 
>> information to recreate the device.  I'm not 100% sure we have that 
>> today but if we solve that problem, it means we can migrate the 
>> device tree during migration which is a feature I'd really like to see.
>
> Why do we need a cold reset at all?  it doesn't map to anything.

That's why I'm suggesting a second-class approach to implementing it if 
someone really wants it.

Regards,

Anthony Liguori