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Thu, 30 Apr 2020 14:11:56 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-113-6.ams2.redhat.com [10.36.113.6]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A24E25C1B0; Thu, 30 Apr 2020 14:11:53 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 2D40811358BC; Thu, 30 Apr 2020 16:11:52 +0200 (CEST) From: Markus Armbruster To: Mark Cave-Ayland Subject: Re: Configuring onboard devices References: <87mu6uia5i.fsf@dusky.pond.sub.org> <20200429155719.GL1495129@redhat.com> <87k11xh2kq.fsf@dusky.pond.sub.org> <87tv11e1en.fsf_-_@dusky.pond.sub.org> <51a4e9ea-eca3-6c1d-a753-86c5810ac094@ilande.co.uk> Date: Thu, 30 Apr 2020 16:11:52 +0200 In-Reply-To: <51a4e9ea-eca3-6c1d-a753-86c5810ac094@ilande.co.uk> (Mark Cave-Ayland's message of "Thu, 30 Apr 2020 11:29:05 +0100") Message-ID: <874kt1dpw7.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=205.139.110.61; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/30 01:04:40 X-ACL-Warn: Detected OS = 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: Kevin Wolf , Peter Maydell , "Daniel P. =?utf-8?Q?Berrang=C3=A9?=" , Eduardo Habkost , Jason Wang , QEMU Developers , Max Reitz , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Mark Cave-Ayland writes: > On 30/04/2020 11:03, Markus Armbruster wrote: >> Peter Maydell writes: >>=20 >>> On Thu, 30 Apr 2020 at 08:09, Markus Armbruster wro= te: >>>> Our means to configure onboard devices are weak. We sidestepped this >>>> for isa-fdc by taking it off the board, and thus make -device work. >>> >>> This seems to be a general dynamic: the x86 pc machine works >>> via -device options (or is changed so it can work that way); >>> and then people propose dropping/deprecating/etc the config >>> options that work with onboard devices, without providing >>> clear solutions/instructions on how the command line needs >>> to change/etc for the mass of boards which are not the x86 >>> pc machine and which do have a lot of onboard devices which >>> can't be handled via -device. >>> >>> So my gut reaction to the "we should deprecate -global" >>> suggestions in this thread was a bit "here we go again"... >>> What works for x86 or even "what is sufficient for libvirt" >>> doesn't necessarily cover all the cases. >>=20 >> Such shortsighted proposals have been made, but don't think it's what >> we're doing here. >>=20 >> You're 100% right in that we do need to configure onboard devices. >> -global is a terrible way to do it, though: it applies to *all* devices >> of a kind. What if the board has more than one? What if the can add >> more? >>=20 >> Taking onboard devices off the board can occasionally sidestep the >> issue. For isa-fdc, we genuinely *wanted* to take the damn thing off, >> because all it did for most users was provide them with VENOM. Not >> needing -global for it anymore was just a nice bonus. >>=20 >> Taking onboard devices off just to reduce the device configuration >> problem to a solved one, namely -device, may be tempting (it was to me), >> but it's too intrusive to be practical at scale. >>=20 >> Adding machine properties that alias onboard device properties is less >> intrusive. The ones I added were still a lot of work. >>=20 >> Configuring onboard devices via machine properties restricts property >> access to the ones we added to the machine. This differs from pluggable >> devices, where users can access all properties. >>=20 >> Any better ideas for letting users configure onboard devices? > > Is it possible to let machine owners add alias properties to the machine = object > referencing in-built devices? I could then instantiate my on-board nic in= the machine > init() function, and then use object_property_add_alias() to add a "nic0"= alias on > the machine that can be used to wire it up to a netdev using the command = line. Have a look at hw/arm/virt.c's virt_flash_create(), from commit e0561e60f1 "hw/arm/virt: Support firmware configuration with -blockdev". It adds machine properties "pflash0" and "pflash1" as aliases for the onboard flash memory devices' property "drive". Does this answer your question?