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-device does not work as -drive do
Copy/paste of https://stackoverflow.com/questions/52929723/qemu-eject-complains-device-is-not-found-while-it-is-there , since I found this bug trying to find an answer to an own question on Stack Overflow.
Below, what was my question the answer I wrote, all exposes the bug.
====================================================================
I need to eject a floppy from QEmu 3.0 monitor, but the command surprisingly fails complaining the device is not found, while it is really there.
Listing of devices:
(qemu) info block
fda: dos-6-22/Dos622-1.img (raw)
Attached to: /machine/unattached/device[11]
Removable device: not locked, tray closed
Cache mode: writeback
hda: hda.img (raw)
Attached to: /machine/peripheral-anon/device[1]
Cache mode: writeback
Eject command result:
(qemu) eject fda
Device 'fda' not found
This is so although this documentation says this is how I have to do: https://www.linux-kvm.org/page/Change_cdrom (just that I want to eject the floppy instead of the CD‑ROM).
The `change` command complains the same:
(qemu) change fda dos-6-22/Dos622-2.img raw
Device 'fda' not found
Is this a bug or me doing something wrong?
I tried using different node names, with always the same result.
====================================================================
I’m posting as an answer, but I’m not strictly sure. I can just say, if I understand correctly, this is a bug.
The answer comes in two parts.
First part, is a stripped down failing invocation:
qemu-system-i386 \
-monitor stdio \
-machine type=isapc,vmport=off \
-blockdev driver=file,node-name=fda-img,filename=fda.img \
-blockdev driver=raw,node-name=fda,file=fda-img \
-global isa-fdc.driveA=fda
(qemu) info block
ide1-cd0: [not inserted]
Attached to: /machine/unattached/device[19]
Removable device: not locked, tray closed
sd0: [not inserted]
Removable device: not locked, tray closed
fda: fda.img (raw)
Attached to: /machine/unattached/device[13]
Removable device: not locked, tray closed
Cache mode: writeback
(qemu) eject fda
Device 'fda' not found
Second part, is the same without the last argument `-global isa-fdc.driveA=fda`:
qemu-system-i386 \
-monitor stdio \
-machine type=isapc,vmport=off \
-blockdev driver=file,node-name=fda-img,filename=fda.img \
-blockdev driver=raw,node-name=fda,file=fda-img
(qemu) info block
ide1-cd0: [not inserted]
Attached to: /machine/unattached/device[19]
Removable device: not locked, tray closed
floppy0: [not inserted]
Attached to: /machine/unattached/device[13]
Removable device: not locked, tray closed
sd0: [not inserted]
Removable device: not locked, tray closed
(qemu) eject floppy0
There is more error when `-global isa-fdc.driveA=fda` is removed. However, the documentation says:
> -global driver=driver,property=property,value=value
> Set default value of driver’s property prop to value, e.g.:
> qemu-system-i386 -global ide-hd.physical_block_size=4096 disk-image.img
> In particular, you can **use this to set driver properties for devices which are created automatically by the machine model**. To create a device which is not created automatically and set properties on it, use -device.
> -global driver.prop=value is shorthand for -global driver=driver,property=prop,value=value. The longhand syntax works even when driver contains a dot.
What I put a stress on in the quote, suggest I’m not misusing `-global` and that’s most probably a bug.
**Update for more details:**
It seems using `-drive` instead of `-device` and `driveA` assignment, the result is not the same, although RedHat documentation recommands using `-device` instead of `-drive` and QEmu 3.0 documentation says `-drive` is essentially a shortcut for `-device` (“essentially”, not telling about the difference).
Below, two cases, with an except of `info block` and an excerpt of `info qtree`.
With this one, `eject floppy0` works:
qemu-system-i386 \
-monitor stdio \
-machine type=isapc,vmport=off \
-drive format=raw,if=floppy,media=disk,file=fda.img \
-device isa-vga,vgamem_mb=1 \
-serial msmouse
[…]
floppy0 (#block156): fda.img (raw)
Attached to: /machine/unattached/device[12]
Removable device: not locked, tray closed
Cache mode: writeback
[…]
dev: isa-fdc, id ""
iobase = 1008 (0x3f0)
irq = 6 (0x6)
dma = 2 (0x2)
driveA = ""
driveB = ""
check_media_rate = true
fdtypeA = "auto"
fdtypeB = "auto"
fallback = "288"
isa irq 6
bus: floppy-bus.0
type floppy-bus
dev: floppy, id ""
unit = 0 (0x0)
drive = "floppy0"
logical_block_size = 512 (0x200)
physical_block_size = 512 (0x200)
min_io_size = 0 (0x0)
opt_io_size = 0 (0x0)
discard_granularity = 4294967295 (0xffffffff)
write-cache = "auto"
share-rw = false
drive-type = "144"
With this one, `eject fda` does not work:
qemu-system-i386 \
-monitor stdio \
-machine type=isapc,vmport=off \
-blockdev driver=file,node-name=fda-img,filename=fda.img \
-blockdev driver=raw,node-name=fda,file=fda-img \
-global isa-fdc.driveA=fda \
-device isa-vga,vgamem_mb=1 \
-serial msmouse
[…]
fda: fda.img (raw)
Attached to: /machine/unattached/device[12]
Removable device: not locked, tray closed
Cache mode: writeback
[…]
dev: isa-fdc, id ""
iobase = 1008 (0x3f0)
irq = 6 (0x6)
dma = 2 (0x2)
driveA = ""
driveB = ""
check_media_rate = true
fdtypeA = "auto"
fdtypeB = "auto"
fallback = "288"
isa irq 6
bus: floppy-bus.0
type floppy-bus
dev: floppy, id ""
unit = 0 (0x0)
drive = "fda"
logical_block_size = 512 (0x200)
physical_block_size = 512 (0x200)
min_io_size = 0 (0x0)
opt_io_size = 0 (0x0)
discard_granularity = 4294967295 (0xffffffff)
write-cache = "auto"
share-rw = false
drive-type = "144"
Hi,
As you yourself say, -drive does work, so this is really not about -drive, but about -blockdev.
-drive creates part of the device as well, so to speak, whereas -blockdev only creates one (or more) nodes in the block layer. You can only eject something from devices, however, so you cannot eject a blockdev. So yes, there is a difference between -drive and -blockdev.
If you want to use eject, you either have to use -drive (which is legacy), or you eject the ID given to -device (because you eject the device). However, you haven't even used -device, but you just used -global (which doesn't allow giving an ID).
As you can see from "info block", there is still a QOM path that you could in theory use, too. So you probably could also "eject /machine/unattached/device[12]" (in the last example).
In practice, you should probably do this:
$ qemu-system-i386 \
-blockdev driver=file,node-name=fda-img,filename=fda.img \
-blockdev driver=raw,node-name=fda,file=fda-img \
-device floppy,id=floppy,drive=fda \
-monitor stdio
(qemu) info block
[...]
fda: fda.img (raw)
Attached to: floppy
Removable device: not locked, tray closed
Cache mode: writeback
(qemu) eject floppy
Device 'floppy' not found
Oops.
Well, it works with QMP:
{'execute':'eject','arguments':{'id':'floppy'}}
{"return": {}}
So there is indeed a bug, although it's not the one you're reporting. The bug is that HMP's eject does not accept a -device ID (but only a -drive ID).
Max
Yes, I messed up with `-device`, because I initially tried to do it with `-device`, later rely only on automatically created device, and so had automatically created devices.
Thanks for you rich comment, I will study it.
The QEMU project is currently considering to move its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state back to "New" within the next 60 days, otherwise this report will be marked as "Expired". Or mark it as "Fix Released" if the problem has been solved with a newer version of QEMU already. Thank you and sorry for the inconvenience.
[Expired for QEMU because there has been no activity for 60 days.]
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