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[149.14.88.106]) by smtp.gmail.com with ESMTPSA id i7sm5113548wrf.67.2022.02.16.23.46.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Feb 2022 23:46:56 -0800 (PST) Message-ID: <45e4f959-8f04-3baf-5e95-d23ed62e4b27@redhat.com> Date: Thu, 17 Feb 2022 08:46:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH 3/3] x86: Switch to q35 as the default machine type To: "Dr. David Alan Gilbert" , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20220215162537.605030-1-dgilbert@redhat.com> <20220215162537.605030-4-dgilbert@redhat.com> <20220216105808.77kqhmsagz3ej74h@sirius.home.kraxel.org> From: Thomas Huth In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=thuth@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=-0.083, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, 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, mst@redhat.com, quintela@redhat.com, qemu-devel@nongnu.org, Gerd Hoffmann , pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 16/02/2022 18.57, Dr. David Alan Gilbert wrote: > * Daniel P. Berrangé (berrange@redhat.com) wrote: >> On Wed, Feb 16, 2022 at 05:40:44PM +0000, Dr. David Alan Gilbert wrote: >>> * Thomas Huth (thuth@redhat.com) wrote: >>>> On 16/02/2022 12.01, Dr. David Alan Gilbert wrote: >>>>> * Gerd Hoffmann (kraxel@redhat.com) wrote: >>>>>> Hi, >>>>>>> Given the semantic differences from 'i440fx', changing the default >>>>>>> machine type has effects that are equivalent to breaking command >>>>>>> line syntax compatibility, which is something we've always tried >>>>>>> to avoid. >>>>>> >>>>>> And if we are fine breaking backward compatibility I'd rather *not* pick >>>>>> a default, effectively making -M $something mandatory, similar to arm. >>>>> >>>>> Oh, that's probably easy to do; what are other peoples thoughts on >>>>> that? >>>> >>>> I agree with Gerd. Getting rid of a default machine on x86 is likely better >>>> than silently changing it to q35. But I'd maybe say that this should go >>>> through the deprecation process first? >>> >>> So just adding something like the following under 'System emulator >>> machines': >>> >>> x86 default machine type >>> ------------------------ >>> >>> x86 currently defaults to the very old ```pc``` machine type >>> which is based on the very old ```i440f``` 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 option is going to take a lot more work switching all the >>> test cases over; in my world here I'd only changed the tests that broke >>> on q35, now everything is going to need to specify a type). >> >> ....which is still nothing compared to how many users will be impacted >> and the docs all over the internet we'll never be able to change, which >> give illustrations using qemu command lines without '-M pc' > > What's your prreference - it sounds like you'd prefer to leave the > default as 'pc' ? > > aarch's message is: > qemu-system-aarch64: No machine specified, and there is no default > Use -machine help to list supported machines > > We could add a: > 'Use -machine pc for the old default behaviour' Sounds like a good idea, but then I'd also do: 'Use -M pc for the old default behaviour, or -M q35 for a more modern machine' or so. Thomas