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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id m13-20020a05600c4f4d00b00386744cb31bsm4441663wmq.35.2022.03.03.10.59.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Mar 2022 10:59:53 -0800 (PST) Date: Thu, 3 Mar 2022 18:59:51 +0000 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH] deprecation: x86 default machine types Message-ID: References: <20220301195432.114252-1-dgilbert@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.1.5 (2021-12-30) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: eduardo@habkost.net, libvir-list@redhat.com, thuth@redhat.com, qemu-devel@nongnu.org, kraxel@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Daniel P. Berrangé (berrange@redhat.com) wrote: > On Wed, Mar 02, 2022 at 07:38:52PM +0000, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > > On Tue, Mar 01, 2022 at 07:54:32PM +0000, Dr. David Alan Gilbert (git) wrote: > > > > From: "Dr. David Alan Gilbert" > > > > > > > > Declare the intent to require a machine type to be specified on x86 > > > > system emulation. > > > > > > > > Signed-off-by: Dr. David Alan Gilbert > > > > --- > > > > docs/about/deprecated.rst | 8 ++++++++ > > > > 1 file changed, 8 insertions(+) > > > > > > > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > > > > index 85773db631..143c60d105 100644 > > > > --- a/docs/about/deprecated.rst > > > > +++ b/docs/about/deprecated.rst > > > > @@ -324,6 +324,14 @@ machine is hardly emulated at all (e.g. neither the LCD nor the USB part had > > > > been implemented), so there is not much value added by this board. Use the > > > > ``ref405ep`` machine instead. > > > > > > > > +x86 default machine type > > > > +'''''''''''''''''''''''' > > > > + > > > > +x86 currently defaults to the ```pc``` machine type which is based on the very > > > > +old ```i440fx``` chipset. This default will be removed and the user will be > > > > +required to specify a machine type explicitly using -M; users are encouraged to > > > > +switch to the not quite as old ```q35``` machine types. > > > > > > This will have no impact on anyone using libvirt as a mgmt app, > > > because it will explicitly set 'pc' if the user doesn't request > > > a machine type. > > > > > > It will, however, break a huge number of users who don't use > > > libvirt or a similar mgmt app. > > > > > > 'q35' is not a drop in replacement for 'pc', and even though > > > it is slightly newer, the features it brings are not likely > > > to be important enough for most users who aren't using a mgmt > > > app to care about switching. > > > > I can see it having advantages for those who do things like PCIe pass > > through of graphics cards. > > However, my main concern is that there's a split happening where > > downstream we're working primarily on q35 but a lot of people still use > > i440fx; eventually that split will mean the i440fx users will have a > > pretty bad experience instability/features. > > So I'd like to encourage them onto a35. > > We've still got quite significant testing coverage of i440fx and outside > of PCI-Express much logic is shared with q35. Right now at least i440fx > feels mature and stable, while q35 is still showing significant > instability with PCI-Express and hotplug in particular. I'd hoppe at > least the combination of maturity of our plain PCI code and testing > coverage would address risk of significant regressions in i440fx even > when attention is on q35. OK, lets drop this for now. > > > In the ongoing work to introduce a completely new system > > > emulator binary that is exclusively runtime QMP configured, > > > the machine type will almost certainly be mandatory, without > > > affecting existing users. That would also apply consistently > > > across all target arches. > > > > I'm assuming that will also cause the disruption to those end users. > > The difference is that people would opt-in to usage of the new system > binaries. So existing users, scripts and documentation won't be impacted > unless they decide to switch - at least as long as we keep the old > system emulators around. If did eventually decide to remove the old > binaries, then there would be disruption but that's more of a clean > break with the past. So I guess that when this happens people will be pushed to the new binaries and the old ones will degrade reasonably fast. Dave > 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 :| > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK