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

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

another showstopper appeared for DVD+RW.

After i disabled SET STREAMING, i was able to write a thoroughly formatted
DVD+RW. But when i inserted one that was never written up to its end, the
attempt failed to (re-)start background formatting (Format Type = 26h):

  FORMAT UNIT
  04 11 00 00 00 00 
  To drive: 12b
  00 02 00 08 ff ff ff ff 98 00 00 01 
  +++ sense data = F0 00 0B 00 00 00 00 0A 00 00 00 00 00 00 00 00 00 00
  +++ key=B  asc=00h  ascq=00h   (   488 ms)

I cannot spot an occurence of this sense code in the qemu sources.
There are B 00 06 , B 29 07 , B 3E 01.

No failed ioctl is reported by my printf.

But the failure happened twice.
After shutdown of the guest (to get access to the drive), i could
format (de-ice) the medium by the host system. Afterwards it was
usable on the booted-again guest.

Currently i suspect that the sense code stems from the guest kernel.
(But caused by some problem with qemu.)


This command can be performed without other preparations.
But its parameters depend on the media state. The one above is
for a partially formatted (i.e. partly written) DVD+RW.

With a completely formatted DVD+RW, the attempt to re-format fails, too:

  FORMAT UNIT
  04 11 00 00 00 00 
  To drive: 12b
  00 02 00 08 ff ff ff ff 98 00 00 00 
  +++ sense data = F0 00 0B 00 00 00 00 0A 00 00 00 00 00 00 00 00 00 00
  +++ key=B  asc=00h  ascq=00h   (   488 ms)

The same command is appropriate for a new, unformatted DVD+RW.
It fails exactly the same way on such a medium. 

The commands here have the Immed bit set (byte 1, bit1 of payload),
so that they should return early. One would watch the drive by
TEST UNIT READY for becomming ready again. REQUEST SENSE with DESC bit
delivers progress information on some drives.
But this is not necessary if FORMAT UNIT already ends with failure
indication.


Have a nice day :)

Thomas