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Date: Wed, 29 Jun 2011 06:03:41 -0400
From: Christoph Hellwig <hch@infradead.org>
Message-ID: <20110629100341.GC22900@infradead.org>
References: <4DEE2B15.4090809@redhat.com> <4DF21447.6090005@suse.de>
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Subject: Re: [Qemu-devel] virtio scsi host draft specification, v3
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christoph Hellwig <chellwig@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel <qemu-devel@nongnu.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Hannes Reinecke <hare@suse.de>, Linux Virtualization <virtualization@lists.linux-foundation.org>

On Wed, Jun 29, 2011 at 10:23:26AM +0200, Paolo Bonzini wrote:
> I agree here, in fact I misread Hannes's comment as "if a driver
> uses more than one queue it is responsibility of the driver to
> ensure strict request ordering".  If you send requests to different
> queues, you know that those requests are independent.  I don't think
> anything else is feasible in the virtio framework.

That doesn't really fit very well with the SAM model.  If we want
to use multiple queues for a single LUN it has to be transparent to
the SCSI command stream.  Then again I don't quite see the use for
that anyway.