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Wed, 18 Nov 2020 14:53:26 +0100 (CET) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Subject: Re: [PATCH for-6.0 1/6] qapi: Add query-accel command References: <20201116131011.26607-1-r.bolshakov@yadro.com> <20201116131011.26607-2-r.bolshakov@yadro.com> <2d934855-ad11-9f61-28a1-7c0a35347a66@redhat.com> <20201116211352.GC1235237@habkost.net> <87mtzgbc29.fsf@dusky.pond.sub.org> <20201118011917.GB10041@SPB-NB-133.local> <87ft57oycu.fsf@dusky.pond.sub.org> <20201118112845.GA11988@merkur.fritz.box> <20201118115612.GD229461@redhat.com> Date: Wed, 18 Nov 2020 14:53:26 +0100 In-Reply-To: <20201118115612.GD229461@redhat.com> ("Daniel P. =?utf-8?Q?Be?= =?utf-8?Q?rrang=C3=A9=22's?= message of "Wed, 18 Nov 2020 11:56:12 +0000") Message-ID: <87blfukbzd.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/18 00:38:29 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Kevin Wolf , Eduardo Habkost , qemu-devel@nongnu.org, Roman Bolshakov , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel P. Berrang=C3=A9 writes: > On Wed, Nov 18, 2020 at 12:28:45PM +0100, Kevin Wolf wrote: >> Am 18.11.2020 um 09:36 hat Markus Armbruster geschrieben: >> > >> >> [...] Even better would b= e >> > >> >> returning an array of KvmInfo with information on all supported >> > >> >> accelerators at once, rather than making the user call this comm= and once >> > >> >> per name. >> > >> > >> > >> > Maybe. It would save us the work of answering the question >> > >> > above, but is this (querying information for all accelerators at >> > >> > once) going to be a common use case? >> > >>=20 >> > >> I recommend to scratch the query-accel parameter, and return inform= ation >> > >> on all accelerators in this build of QEMU. Simple, and consistent = with >> > >> similar ad hoc queries. If a client is interested in just one, fis= hing >> > >> it out of the list is easy enough. >> > >>=20 >> > > >> > > Works for me. I'll then leave KvmInfo as is and will introduce Accel= Info >> > > with two fields: name and enabled. enabled will be true only for >> > > currently active accelerator. >> >=20 >> > Please document that at most on result can have 'enabled': true. >>=20 >> This doesn't feel right. >>=20 >> If I understand right, the proposal is to get a result like this: >>=20 >> [ { 'name': 'kvm', 'enabled': true }, >> { 'name': 'tcg', 'enabled': false }, >> { 'name': 'xen', 'enabled': false } ] >>=20 >> The condition that only one field can be enabled would only be in the >> documentation instead of being enforced. >>=20 >> Instead, consider a response like this: >>=20 >> { 'available': [ 'kvm', 'tcg', 'xen' ], >> 'active': 'kvm' } >>=20 >> This is not only shorter, but also makes sure that only one accelerator >> can be reported as active. Better. Documentation only, not enforced: no duplicate array elements. We got that elsewhere already (arrays used as sets, basically). If we want to provide for reporting additional information on available accelerators, tweak it to {"available": [{"name": "kvm"}, {"name": "tcg"}, {"name": "xen"}], "active": "kvm"} If accelerator-specific extra information is needed, the array elements can compatibly evolve into flat unions. Another way to skin this cat: {"available": {"kvm": { extra properties... }, "tcg": ..., "xen": ...}, "active": "kvm"} No need for unions then. "No dupes" is enforced. We could inline "available": {"kvm": { extra properties... }, "tcg": ..., "xen": ..., "active": "kvm"} Future accelerators can't be named "active" then. > I guess this can be extended with a union to report extra props for the > accelerator, discriminated on the 'active' field eg > > { 'available': [ 'kvm', 'tcg', 'xen' ], > 'active': 'kvm', > 'data': { > "allow-nested": true, > } > } Correct.