Re: [Qemu-devel] [PATCH 1/3] scsi-disk: close drive on START_STOP

[Markus Armbruster]

Markus Armbruster <address@hidden> writes:

> Paolo Bonzini <address@hidden> writes:
>
>> Il 04/12/2013 05:55, Alexey Kardashevskiy ha scritto:
>>> Normally the user is expected to eject DVD if it is not locked by
>>> the guest. eject_device() makes few checks and calls bdrv_close()
>>> if DVD is not in use.
>>> 
>>> However it is still possible to eject DVD even if it is in use.
>>> For that, QEMU sets "eject requested" flag, the guest reads it, issues
>>> ALLOW_MEDIUM_REMOVAL(enable=1) and START_STOP(start=0). But in this case,
>>> bdrv_close() is not called anywhere so it remains "inserted" in QEMU's
>>> terms.
>>
>> This is expected behavior, and matches what IDE does.
>>
>> Markus, can you confirm?
>
> Confirmed.  See commit 4be9762.
>
> Alexey, monitor commands eject does two things: it first opens the tray,
> and if that works, it removes the medium.
>
> If the tray is locked closed, it tells the device model that eject was
> requested.  Works just like the physical eject button.
>
> With -f, it then rips out the medium.  This is similar to opening the
> tray with a unbent paperclip.  Let's ignore this case.
>
> The scsi-cd device model tells the guest about the eject request.  A
> well-behaved guest will then command the device to unlock and open the
> tray.
>
> The guest uses the same commands on behalf of its applications,
> e.g. /usr/bin/eject.
>
> Your patch changes behavior of "eject /dev/sr0 && eject -t /dev/sr0":
> you no longer get the same medium back.  You normally do with real
> hardware.

Alexey asked me for details on IRC.

    $ qemu -nodefaults -monitor stdio -S -machine accel=kvm -m 512 -display 
vnc=:0 -device cirrus-vga -drive if=none,id=disk,file=test.qcow2 -device 
ide-hd,drive=disk,bus=ide.0 -drive if=none,id=cd,file=f16.iso -device 
ide-cd,drive=cd,bus=ide.1
    QEMU 1.7.50 monitor - type 'help' for more information
    (qemu) info block cd

    cd: f16.iso (raw)
        Removable device: not locked, tray closed

Boot the guest (Fedora 16, no X)

    (qemu) c

The guest locked the tray:

    (qemu) info block cd

    cd: f16.iso (raw)
        Removable device: locked, tray closed

In the guest, log in as root on the console, and run

    # eject /dev/sr0

Makes the guest open the tray:

    (qemu) info block cd

    cd: f16.iso (raw)
        Removable device: locked, tray open

In the guest, run

    # eject -t /dev/sr0

Makes the guest close the tray:

    (qemu) info block cd

    cd: f16.iso (raw)
        Removable device: locked, tray closed

Verify the guest can access the medium:

    # mount -r /dev/sr0 /mnt

> The somewhat unfortunate consequence is that monitor command eject can
> only remove the medium when the tray is not locked.