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Thu, 6 Feb 2020 20:59:48 +0000 (UTC) Date: Thu, 6 Feb 2020 15:59:48 -0500 From: Eduardo Habkost To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [Qemu-devel] [PATCH v5 1/6] machine: Convert the valid cpu types to use cpu_model Message-ID: <20200206205948.GD412524@habkost.net> References: <62d7649e-e85d-43a2-2df8-85e2a0953e89@redhat.com> <20190617170106.48d776ca@redhat.com> <0a31228d-4d32-2c54-649b-6aef9953fffc@redhat.com> <20190617173343.68e3c9ec@redhat.com> <20190617162700.GC19178@habkost.net> <20190618133410.18b93bcd@redhat.com> <20190618135516.GH19178@habkost.net> <20190620110239.6c4c092d@redhat.com> <20190620144328.GA1862@habkost.net> <87908f05-f14a-c502-db0b-96f849d018d1@redhat.com> MIME-Version: 1.0 In-Reply-To: <87908f05-f14a-c502-db0b-96f849d018d1@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: HwzfMRZXN3q2z_aJQj_tGw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: peter.maydell@linaro.org, Markus Armbruster , qemu-devel@nongnu.org, alistair23@gmail.com, marcel@redhat.com, Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jan 23, 2020 at 07:48:21PM +0100, Philippe Mathieu-Daud=E9 wrote: > On 6/20/19 4:43 PM, Eduardo Habkost wrote: > > On Thu, Jun 20, 2019 at 11:02:39AM +0200, Igor Mammedov wrote: > > > On Tue, 18 Jun 2019 10:55:16 -0300 > > > Eduardo Habkost wrote: > > >=20 > > > > On Tue, Jun 18, 2019 at 01:34:10PM +0200, Igor Mammedov wrote: > > > > > On Mon, 17 Jun 2019 13:27:00 -0300 > > > > > Eduardo Habkost wrote: > > > > > > On Mon, Jun 17, 2019 at 05:33:43PM +0200, Igor Mammedov wrote: > > > > > > > On Mon, 17 Jun 2019 17:15:21 +0200 > > > > > > > Philippe Mathieu-Daud=E9 wrote: > > > > > > [...] > > > > > > > > Yes. Eduardo and you should write some lines to explain thi= s, and then > > > > > > > > we will follow :) > > > > > > > Unfortunately I don't recall details anymore. One could check= out all > > > > > > > implementations of class_by_name callbacks to find out curren= t state. > > > > > >=20 > > > > > > See this message for a summary of existing class_by_name quirks= : > > > > > >=20 > > > > > > https://www.mail-archive.com/qemu-devel@nongnu.org/msg615503= .html > > > > > > Date: Wed, 08 May 2019 10:34:44 +0200 > > > > > > Message-ID: <877eb173a3.fsf@dusky.pond.sub.org> > > > > > > Subject: Re: [Qemu-devel] [PATCH 0/7] Delete 16 *_cpu_class_= by_name() functions > > > > > >=20 > > > > > > I'm unsure about Igor's suggestion to get rid of CPU model name= s > > > > > > and use only QOM type names in external interfaces. In either > > > > > > case, we can still simplify the rules rules and reduce the amou= nt > > > > > > of arch-specific code. > > > > > as far as we have cpu_class_by_name, we have to watch over that > > > > > new patches/targets won't add some custom handling/fallbac/whatno= t. > > > >=20 > > > > We can get rid of CPUClass::cpu_class_by_name() without changing > > > > the external interfaces provided by QEMU. > > > if you mean QMP, than it is possible to keep model there where > > > it already exists. Based on experiment [1](x86) I did, it's local to > > > affected target and doesn't pollute other code. > >=20 > > I mean both command line and QMP. > >=20 > > >=20 > > > > I don't have a strong opinion about using only QOM types at -cpu, > > > > yet. But first we need to get rid of the arch-specific CPU model > > > > name exceptions enumerated at the URL above (which would be very > > > > welcome). > > > One way to get rid of them is to deprecate them in favor of strict > > > match (no fallback/substitutions/aliases) to typename and when we > > > drop it make switch type based naming only. > >=20 > > This is true, but is it desirable? Aren't we just moving > > complexity elsewhere? Management software would still need to > > translate CPU models from existing VM configurations to QOM type > > names. > >=20 > > >=20 > > > 1) I've just took a quick look at how much of duplicated/confusing > > > code we could get rid off if we drop cpu_class_by_name/*_cpu_list. > > > It amounts to >800LOC of trivial removal (not counting ppc/s390 > > > that depend on model naming heavily and in need of some non > > > trivial refactoring) > >=20 > > Removing the code might be trivial. Coordinating with the > > maintainers of all architectures to confirm this is really > > something everybody wants is the difficult part. > >=20 > > If you really want to do it, please make sure all the > > architecture maintainers (and libvirt developers) are involved in > > the discussion. >=20 > From the previous link (summary of existing class_by_name quirks): > https://www.mail-archive.com/qemu-devel@nongnu.org/msg615737.html >=20 > "Deprecating unwanted stuff now is likely to make a > later cleanup so much easier." >=20 > This was 8 months ago :/ >=20 > IIUC we need to restart this topic addressing the libvirt community first= , > then see with the QEMU one? The next step is to deprecate the weird and pointless exceptions listed at the URL you mentioned. Not all exceptions will affect libvirt (m= aybe most won't). In either case, we can just use qemu-deprecated.texi to communicate this to libvirt developers. MAINTAINERS already has a "R: libvir-list" line for qemu-deprecated.texi. --=20 Eduardo