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[2001:4830:134:3::11]) by mx.google.com with ESMTPS id x32-v6si4850500qtx.59.2018.06.14.02.00.10 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 14 Jun 2018 02:00:10 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) client-ip=2001:4830:134:3::11; Authentication-Results: mx.google.com; spf=pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) smtp.mailfrom="qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([::1]:39305 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTO70-000138-6e for alex.bennee@linaro.org; Thu, 14 Jun 2018 05:00:10 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43229) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTO6u-000131-Bc for qemu-arm@nongnu.org; Thu, 14 Jun 2018 05:00:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTO6r-0001ID-9s for qemu-arm@nongnu.org; Thu, 14 Jun 2018 05:00:04 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:56480 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fTO6r-0001GK-5X; Thu, 14 Jun 2018 05:00:01 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 894E6738E0; Thu, 14 Jun 2018 09:00:00 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 89E372166BB3; Thu, 14 Jun 2018 08:59:57 +0000 (UTC) Date: Thu, 14 Jun 2018 09:59:54 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Laszlo Ersek Message-ID: <20180614085954.GM6355@redhat.com> References: <1528879723-24675-1-git-send-email-eric.auger@redhat.com> <1528879723-24675-10-git-send-email-eric.auger@redhat.com> <8bf1bccc-b32a-9982-6123-b644c41a96d3@redhat.com> <33a3fa10-bf1a-45cd-73bd-403cbd8d4792@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.5 (2018-04-13) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Thu, 14 Jun 2018 09:00:00 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Thu, 14 Jun 2018 09:00:00 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'berrange@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: Re: [Qemu-arm] [Qemu-devel] [PATCH 9/9] hw/arm/virt: Add virt-3.0 machine type X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: peter.maydell@linaro.org, drjones@redhat.com, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, qemu-devel@nongnu.org, christoffer.dall@arm.com, Auger Eric , qemu-arm@nongnu.org, zhaoshenglong@huawei.com, eric.auger.pro@gmail.com Errors-To: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-arm" X-TUID: 1DcJ0OfyY4jh On Thu, Jun 14, 2018 at 10:56:20AM +0200, Laszlo Ersek wrote: > Hi Eric, > > On 06/14/18 08:27, Auger Eric wrote: > > Hi Laszlo, > > > > On 06/13/2018 11:05 PM, Laszlo Ersek wrote: > >> On 06/13/18 10:48, Eric Auger wrote: > >> > >>> PATCH: merge of ECAM and VCPU extension > >>> - Laszlo reviewed the ECAM changes but I dropped his R-b > >>> due to the squash > >> > >> Was there any particular reason why the previous patch set (with only > >> the ECAM enlargement) couldn't be merged first? To be honest I'm not > >> super happy when my R-b is dropped for non-technical reasons; it seems > >> like wasted work for both of us. > >> > >> Obviously if there's a technical dependency or some other reason why > >> committing the ECAM enlargement in separation would be *wrong*, that's > >> different. Even in that case, wouldn't it be possible to keep the > >> initial virt-3.0 machtype addition as I reviewed it, and then add the > >> rest in an incremental patch? > > > > Sorry about that. My fear was about migration. We would have had 2 virt > > 3.0 machine models not supporting the same features. While bisecting > > migration we could have had the source using the high mem ECAM and the > > destination not supporting it. So I preferred to avoid this trouble by > > merging the 2 features in one patch. However I may have kept your R-b > > restricting its scope to the ECAM stuff. > > to my understanding, it is normal to *gradually* add new properties > during the development cycle, to the new machine type of the upcoming > QEMU release. To my understanding, it's not expected that migration work > between development snapshots built from git. What matters is that two > official releases, specifying the same machine type, enable the user to > migrate a guest between them (in forward direction). > > In every release, so many new features are introduced that it's > impossible to introduce the new machine type with all the compat knobs > added at once. Instead, the new machine type is introduced when the > first feature that requires a compat knob is added to git. All other > such features extend the compat knobs gradually, during the development > cycle. Until the new official release is made (which contains all the > compat knobs for all the new features), the new machine type simply > doesn't exist, as far as the public is concerned, so it cannot partake > in migration either. > > This is my understanding anyway. That is correct - there is ZERO expectation of migration / ABI stability between arbitrary GIT snapshots, only official releases. Prior to the first release including it, a versioned machine type can be changed arbitrarily. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43260) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTO71-000186-Gk for qemu-devel@nongnu.org; Thu, 14 Jun 2018 05:00:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTO6v-0001Pk-RH for qemu-devel@nongnu.org; Thu, 14 Jun 2018 05:00:11 -0400 Date: Thu, 14 Jun 2018 09:59:54 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180614085954.GM6355@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <1528879723-24675-1-git-send-email-eric.auger@redhat.com> <1528879723-24675-10-git-send-email-eric.auger@redhat.com> <8bf1bccc-b32a-9982-6123-b644c41a96d3@redhat.com> <33a3fa10-bf1a-45cd-73bd-403cbd8d4792@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH 9/9] hw/arm/virt: Add virt-3.0 machine type List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: Auger Eric , eric.auger.pro@gmail.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, peter.maydell@linaro.org, wei@redhat.com, drjones@redhat.com, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, christoffer.dall@arm.com, zhaoshenglong@huawei.com On Thu, Jun 14, 2018 at 10:56:20AM +0200, Laszlo Ersek wrote: > Hi Eric, > > On 06/14/18 08:27, Auger Eric wrote: > > Hi Laszlo, > > > > On 06/13/2018 11:05 PM, Laszlo Ersek wrote: > >> On 06/13/18 10:48, Eric Auger wrote: > >> > >>> PATCH: merge of ECAM and VCPU extension > >>> - Laszlo reviewed the ECAM changes but I dropped his R-b > >>> due to the squash > >> > >> Was there any particular reason why the previous patch set (with only > >> the ECAM enlargement) couldn't be merged first? To be honest I'm not > >> super happy when my R-b is dropped for non-technical reasons; it seems > >> like wasted work for both of us. > >> > >> Obviously if there's a technical dependency or some other reason why > >> committing the ECAM enlargement in separation would be *wrong*, that's > >> different. Even in that case, wouldn't it be possible to keep the > >> initial virt-3.0 machtype addition as I reviewed it, and then add the > >> rest in an incremental patch? > > > > Sorry about that. My fear was about migration. We would have had 2 virt > > 3.0 machine models not supporting the same features. While bisecting > > migration we could have had the source using the high mem ECAM and the > > destination not supporting it. So I preferred to avoid this trouble by > > merging the 2 features in one patch. However I may have kept your R-b > > restricting its scope to the ECAM stuff. > > to my understanding, it is normal to *gradually* add new properties > during the development cycle, to the new machine type of the upcoming > QEMU release. To my understanding, it's not expected that migration work > between development snapshots built from git. What matters is that two > official releases, specifying the same machine type, enable the user to > migrate a guest between them (in forward direction). > > In every release, so many new features are introduced that it's > impossible to introduce the new machine type with all the compat knobs > added at once. Instead, the new machine type is introduced when the > first feature that requires a compat knob is added to git. All other > such features extend the compat knobs gradually, during the development > cycle. Until the new official release is made (which contains all the > compat knobs for all the new features), the new machine type simply > doesn't exist, as far as the public is concerned, so it cannot partake > in migration either. > > This is my understanding anyway. That is correct - there is ZERO expectation of migration / ABI stability between arbitrary GIT snapshots, only official releases. Prior to the first release including it, a versioned machine type can be changed arbitrarily. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|