linux-kernel - Re: VIRTIO_BLK_T_SCSI_CMD handling in virtio-blk

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Message-ID: <49C0BBFB.5040605@suse.de>
Date:	Wed, 18 Mar 2009 10:16:43 +0100
From:	Hannes Reinecke <hare@...e.de>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Anthony Liguori <aliguori@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: VIRTIO_BLK_T_SCSI_CMD handling in virtio-blk

Christian Borntraeger wrote:
> Am Wednesday 18 March 2009 07:09:19 schrieb Christoph Hellwig:
>> Currently virtio-blk just sends down the payload for packet command
>> requests, setting the VIRTIO_BLK_T_SCSI_CMD flag in the type field and
>> zeroing out the sector field.
>>
>> But to make any sense of the payload of a packet command we need the
>> scsi command block (request->cmd) which specifies the operation,
>> location and length for this command.
>>
>> All backends that I checked just fail VIRTIO_BLK_T_SCSI_CMD commands, so
>> AFAICS no harm is done.  But should we really keep this broken support
>> in the protocol around?  If we do want to support packet commands in
>> the future we should probably just add the command as the first S/G list
>> entry.
> 
> Hannes did some implementation for SCSI command passthrough:
> https://lists.linux-foundation.org/pipermail/virtualization/2008-August/011629.html
> 
> After some addon fix this was working pretty well. I dont know why Hannes never
> pushed the final version upstream.
> 
Sorry, being busy. Someone keeps sending me multipath bugs to worry about.
Patch is attached.

Please do keep me in the loop here, I'm not subscribed to lkml.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@...e.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)

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