Re: [Qemu-devel] Do you have a use for a tester of virtio-scsi with CD drives ?

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/05/2011 03:37 PM, Thomas Schmitt wrote:
> MMC-3 5.2 and MMC-5 6.2.3 state about processing of command BLANK with
> Immed bit set to one:
> "In response to the REQUEST SENSE command, unless an error has occurred,
>   the Drive shall return a SK/ASC/ASCQ values set to
>   NOT READY/LOGICAL UNIT NOT READY/OPERATION IN PROGRESS,
>   with the sense key specific bytes set for progress indication."
>
> But libburn gets on qemu
>
>    TEST UNIT READY
>    00 00 00 00 00 00
>    +++ sense data = 71 00 02 00 00 00 00 0A 00 00 00 00 04 08 00 80 24 8B
>    +++ key=2  asc=04h  ascq=08h   (     0 ms)
>
>    REQUEST SENSE
>    03 00 00 00 12 00
>    From drive: 18b
>    f0 00 00 00 00 00 00 0a 00 00 00 00 00 00 00 00 00 00
>         0 ms
>
> It is ok that TEST UNIT READY reports the sense data with
>    2 04 08 LOGICAL UNIT NOT READY, LONG WRITE IN PROGRESS
> But it is not ok that REQUEST SENSE does not do the same.
> On qemu it reports:
>    0 00 00 NO ADDITIONAL SENSE INFORMATION

This is because QEMU always emulates REQUEST SENSE and always returns 
the sense data from the last request.  Is this git master or 0.15?  For 
git master, I would have expected REQUEST SENSE to return the correct 
sense data, but without updating it.

In general, it seems safer (and simpler?) if libburn uses TEST UNIT 
READY and its autosense data to report progress.  REQUEST SENSE would be 
used if SG_IO reports CHECK CONDITION without SG_ERR_DRIVER_SENSE (but 
modern OSes will always emulate autosense even if the HBA does not 
support it) and possibly if TEST UNIT READY returns GOOD which is 
allowed by deprecated in MMC.

Paolo