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Wed, 14 Apr 2021 09:06:09 +0200 (CEST) From: Markus Armbruster To: Adam Williamson <1923663@bugs.launchpad.net> Subject: Re: [Bug 1923663] [NEW] Can't(?) disable default floppy drive any more in qemu 6.0 References: <161834460731.13851.12350778402155141357.malonedeb@chaenomeles.canonical.com> Date: Wed, 14 Apr 2021 09:06:09 +0200 In-Reply-To: <161834460731.13851.12350778402155141357.malonedeb@chaenomeles.canonical.com> (Adam Williamson's message of "Tue, 13 Apr 2021 20:10:07 -0000") Message-ID: <87fsztny5a.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 10.5.11.15 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 Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H4=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: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Adam Williamson <1923663@bugs.launchpad.net> writes: > Public bug reported: > > There's a documented change in qemu 6.0: > > https://qemu-project.gitlab.io/qemu/system/removed-features.html#floppy- > controllers-drive-properties-removed-in-6-0 > > where you can't configure floppy controller device properties with > -global any more. However, there's a thing you could do with the old > parameter which I can't figure out a way to do with the documented > replacement. openQA passed exactly this argument: > > -global isa-fdc.driveA= > > and that has the effect of removing/disabling the default floppy > drive/controller. If you just run `qemu-system-i686` (no other args) > you'll see the VM briefly try to boot from a floppy drive; if you run > `qemu-system-i686 -global isa-fdc.driveA=` (with an earlier version of > qemu, obviously) you'll see it does not do so. > > I can't see a way to do this with `-device floppy`. Going by the docs, > the equivalent should be: > > -device floppy,unit=0,drive= > > but that does not seem to have the same effect. If you run `qemu- > system-i686 -device floppy,unit=0,drive=`, it still tries to boot from a > floppy drive. > > I see there's a -nodefaults option that disables *all* default devices, > but I don't think that's what we want here either. We might want the > other default devices, we just don't want the floppy drive. = Short answer = In my opinion, management applications are better off with -nodefaults. It's easier to understand than the complicated mess I'm going to describe under "Long answer" below. If you'd prefer not to, try -global isa-fdc.fdtypeA=none. = Long answer = -global isa-fdc.driveA= worked. Whether it was supported usage or accidental dirt effect is unclear. Doesn't matter now. -nodefaults suppresses a number of backends: * Character device backend for a serial device Also suppressed when -serial ... or -device isa-serial,... or -global isa-serial.PROP=VAL is given, or the machine type opts out of this backend. Backend configuration depends on other options; too complicated to explain here. * Character device backend for a parallel device Also suppressed when -parallel ... or -device isa-parallel,... or -global isa-parallel.PROP=VAL is given, or the machine type opts out of this backend. Backend configuration depends on other options; too complicated to explain here. * Block device backend a floppy device Also suppressed when -device isa-fdc,... or -global isa-fdc.PROP=VAL or -device floppy or -global floppy.PROP=VAL is given, or the machine type opts out of this backend. * Block device backend a CD-ROM device Also suppressed when -device {ide,scsi}-{cd,hd},... or -global {ide,scsi}-{cd,hd}.PROP=VAL is given, or the machine type opts out of this backend. * SD card Also suppressed when the machine type opts out of this backend. When a backend exists, the machine type may * Create a frontend (a.k.a. device model) connected to the backend * Ignore the backend silently * Complain about the useless backend -nodefaults additionally suppresses: * Default HMP monitor Also suppressed when -monitor or -qmp or -qmp-pretty or -mon or -serial mon:... or -parallel mon:... is given. Monitor configuration depends on other options; too complicated to explain here. * Default network frontend (-net nic) and backend (-net user) Also suppressed when -netdev or -nic or -net is given. Default backend is only done when we have SLIRP. * Default VGA type, if any Actual type depends on the machine machine type. Set to "none" when -vga or -device DRV,... or -global DRV.PROP=VAL is given, where DRV is a VGA device model. When the type is not "none", the machine type may: * Create a device of that type * Ignore the type silently * Complain about the type * Additional stuff depending on the machine type Questions?