Re: [Bug 1923663] [NEW] Can't(?) disable default floppy drive any more in qemu 6.0

[Peter Maydell <1923663@bugs.launchpad.net>]

On Wed, 14 Apr 2021 at 08:07, Markus Armbruster <armbru@redhat.com> wrote:
> 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.

Is there a mechanism to get QEMU to tell me "what are all the
long options I need to specify explicitly now to get the same
behaviour that I had before I started passing -nodefaults" ?
Otherwise it's a pretty painful route to suggest that people
go down (though I agree that for a management app as opposed to
an individual user it's probably a worthwhile route in the long
term).

-- PMM

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https://bugs.launchpad.net/bugs/1923663

Title:
  Can't(?) disable default floppy drive any more in qemu 6.0

Status in QEMU:
  New

Bug description:
  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.

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