Re: [Qemu-ppc] Bug with REPORT LUNS in IBM VSCSI

[Paolo Bonzini]

Il 02/10/2013 17:33, Nathan Whitehorn ha scritto:
> On 10/02/13 10:17, Paolo Bonzini wrote:
>> Il 02/10/2013 17:12, Nathan Whitehorn ha scritto:
>>> I'm having some trouble with the VSCSI emulation in the pSeries machine.
>>> It seems that the emulated SCSI target device on the SRP IT_nexus
>>> properly distributes SCSI commands to its children but does not report
>>> them in response to a REPORT LUNS request. This happens because it
>>> forwards REPORT LUNs to target 0 on its child bus instead of answering
>>> the command itself.
>> How so?  The SCSI emulation hijacks REPORT_LUNS and does not pass it
>> down to the device's alloc_req callback, but the request is still
>> processed as if it came to the device.
>>
>> Can you give QEMU's command-line?  Can you reproduce the same bug with
>> an x86 FreeBSD guest using virtio-scsi?
> 
> The issue is that VSCSI SRP has only one direct target port and then
> uses hierarchical LUNs to pass requests further down the bus using the
> LUN addressing method. My understanding of SAM5 is that the emulated
> target device should report all of those sub-LUNs, on all sub-targets,
> in response to a REPORT LUNS command addressed to LUN 0 on the only
> direct target. Is that correct?

Interesting.  So you're saying that FreeBSD expects the returned list of
LUNs to use the logical unit addressing method?

Both Linux and Windows scan each channel separately.  Linux, in
addition, does not expect REPORT LUNS to use the logical unit addressing
method in the returned list of LUNs.  The driver converts the
channel/target/LUN tuple to that addressing method when it builds the
SRP commands.

Paolo