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[209.51.188.17]) by mx.google.com with ESMTPS id h14si17715328ejx.140.2019.07.31.03.18.53 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 31 Jul 2019 03:18:54 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; spf=pass (google.com: domain of qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([::1]:39550 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hslh7-00020v-7u for alex.bennee@linaro.org; Wed, 31 Jul 2019 06:18:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55366) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hslgg-0001WI-TF for qemu-devel@nongnu.org; Wed, 31 Jul 2019 06:18:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hslgf-0000tY-SC for qemu-devel@nongnu.org; Wed, 31 Jul 2019 06:18:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60424) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hslgb-0000qv-7P; Wed, 31 Jul 2019 06:18:21 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0F07985540; Wed, 31 Jul 2019 10:18:20 +0000 (UTC) Received: from ptitpuce (ovpn-116-130.ams2.redhat.com [10.36.116.130]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 541B65D6A7; Wed, 31 Jul 2019 10:17:53 +0000 (UTC) References: <20190729145654.14644-1-damien.hedde@greensocs.com> <20190729145654.14644-2-damien.hedde@greensocs.com> <20190730154209.2049f10a.cohuck@redhat.com> <20190730155547.7b201f5e.cohuck@redhat.com> User-agent: mu4e 1.3.2; emacs 26.2 From: Christophe de Dinechin To: qemu-devel@nongnu.org In-reply-to: Date: Wed, 31 Jul 2019 12:17:50 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 31 Jul 2019 10:18:20 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v3 01/33] Create Resettable QOM interface X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Collin Walling , Dmitry Fleytman , "Michael S. Tsirkin" , Mark Cave-Ayland , Gerd Hoffmann , Edgar Iglesias , Hannes Reinecke , Qemu-block , David Hildenbrand , Halil Pasic , Christian Borntraeger , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , David Gibson , Thomas Huth , Eduardo Habkost , Alistair Francis , qemu-s390x , qemu-arm , =?utf-8?Q?C=C3=A9dric?= Le Goater , John Snow , Richard Henderson , Damien Hedde , "Daniel P. Berrange" , Cornelia Huck , Mark Burton , qemu-ppc , Paolo Bonzini Errors-To: qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-devel" X-TUID: TUjYWNmx/DtB Peter Maydell writes: > On Tue, 30 Jul 2019 at 14:56, Cornelia Huck wrote: >> >> On Tue, 30 Jul 2019 14:44:21 +0100 >> Peter Maydell wrote: >> >> > On Tue, 30 Jul 2019 at 14:42, Cornelia Huck wrote: >> > > I'm having a hard time figuring out what a 'cold' or a 'warm' reset is >> > > supposed to be... can you add a definition/guideline somewhere? >> > >> > Generally "cold" reset is "power on" and "warm" is "we were already >> > powered-on, but somebody flipped a reset line somewhere". >> >> Ok, that makes sense... my main concern is to distinguish that in a >> generic way, as it is a generic interface. What about adding something >> like: >> >> "A 'cold' reset means that the object to be reset is initially reset; a 'warm' >> reset means that the object to be reset has already been initialized." >> >> Or is that again too generic? > > I think it doesn't quite capture the idea -- an object can have already > been reset and then get a 'cold' reset: this is like having a powered-on > machine and then power-cycling it. > > The 'warm' reset is the vaguer one, because the specific behaviour > is somewhat device-dependent (many devices might not have any > difference from 'cold' reset, for those that do the exact detail > of what doesn't get reset on warm-reset will vary). But every > device should have some kind of "as if you power-cycled it" (or > for QEMU, "go back to the same state as if you just started QEMU on the > command line"). Our current "reset" method is really cold-reset. Is there any concept of locality associated with warm reset? For example, you'd expect a cold reset to happen on the whole system, but I guess a warm reset could be restricted to a single bus. The documentation should give examples of how warm reset could be triggered, and what it could do differently from cold reset. > > thanks > -- PMM -- Cheers, Christophe de Dinechin (IRC c3d)