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

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/04/2011 12:09 PM, Thomas Schmitt wrote:
> So there are still two show stoppers.
>
> DVD+RW gets stuck at SET STREAMING.
> (I will hack libburn to avoid this command and check whether
>   writing is possible then. Chances are good, as writing an
>   already formatted DVD+RW is quite artless.)
>
> CD SAO gets stuck at SEND CUE SHEET.
> (SAO is possible with blank CDs only. It is desirable, because its
>   results do not show the traditional read-ahead bug of Linux, which
>   is caused by the two non-data sectors at the end of TAO tracks.)

Is this okay to send to a blank CD with no prior command?  That is, can 
I simply change your SEND CUE SHEET dump to "sg_raw -s" to reproduce?

> Do you have any hints where i should dig for the special processing
> of these commands, which obviously suffer timeout after 200 seconds,
> and then drive qemu or the guest into a busily unusable state ?
>
> There must be something about them in qemu. On the host they work
> flawlessly.
> Both send data, but so do SET CD SPEED, MODE SELECT(10), WRITE(10)
> which work fine on the guest.

I wouldn't be surprised if they are bugs in either scsi-generic or the 
LSI emulation code.  They seem to occur when commands return less data 
than the guest driver has asked; with master I get a guest oops in the 
LSI driver, while the host pads the return data with zeros.  Your READ 
DISC STRUCTURE work for me with my (out-of-tree) vmw_pvscsi emulation.

Paolo