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[88.26.246.243]) by smtp.gmail.com with ESMTPSA id d1sm8136972ejy.3.2020.01.07.06.20.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Jan 2020 06:20:42 -0800 (PST) Subject: Re: Priority of -accel To: Thomas Huth , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Paolo Bonzini References: <20200106130951.29873-1-philmd@redhat.com> <12334054-4ae7-e580-9727-2d322bfa2bda@redhat.com> <58eb34db-7d32-8b0e-d9ef-98648209486b@redhat.com> <656169fc-1abe-b521-20a3-e7041739b914@redhat.com> <20200107125451.GL3368802@redhat.com> <3241dff4-6223-404f-55d4-846991763046@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <2ae2dee3-cd16-a247-971b-4b3482e596a5@redhat.com> Date: Tue, 7 Jan 2020 15:20:40 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <3241dff4-6223-404f-55d4-846991763046@redhat.com> Content-Language: en-US X-MC-Unique: v1Lv76zFP6SHU23GZxbtIw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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 , qemu-block@nongnu.org, qemu-devel@nongnu.org, Markus Armbruster , Wainer dos Santos Moschetta , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/7/20 3:14 PM, Thomas Huth wrote: > On 07/01/2020 13.54, Daniel P. Berrang=C3=A9 wrote: >> On Tue, Jan 07, 2020 at 01:23:18PM +0100, Paolo Bonzini wrote: >>> On 07/01/20 13:18, Thomas Huth wrote: >>>> I don't think we need a separate priority parameter here. But IMHO it'= s >>>> really rather common practice to prioritize the last option. So whil= e >>>> it might be more "self-explanatory" to a CLI newbie if the first >>>> occurrence got the highest priority, it might be rather confusing >>>> instead for a CLI veteran...? >>> >>> Prioritising the last certainly makes sense for a choose-one-only >>> option, but I'm not sure it's the same for a choose-best option. After >>> all it was -machine accel=3Dkvm:tcg, not -machine accel=3Dtcg:kvm... >> >> IIUC, the main use case for specifying multiple accelerators is >> so that lazy invokations can ask for a hardware virt, but then get >> fallback to TCG if not available. For things that should be platform >> portabile, there's more than just kvm to consider though, as we have >> many accelerators. Listing all possible accelerators is kind of >> crazy though no matter what the syntax is. >> >> How about taking a completely different approach, inspired by the >> -cpu arg and implement: >> >> -machine accel=3Dbest >=20 > Something like that sounds like the best solution to me, but I'd maybe > rather not call it "best", since the definition of "best" might depend > on your use-case (e.g. do you want to use a CPU close to the host or > something different which might be better emulated by TCG?). >=20 > What about "-accel any" or "-accel fastest" or something similar? 'any' is a russian roulette, you don't want it to return 'qtest' ;)