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Re: [Qemu-devel] virtio scsi host draft specification, v3


From: Paolo Bonzini
Subject: Re: [Qemu-devel] virtio scsi host draft specification, v3
Date: Wed, 29 Jun 2011 12:35:51 +0200
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Mnenhy/0.8.3 Thunderbird/3.1.10

On 06/29/2011 12:31 PM, Michael S. Tsirkin wrote:
On Wed, Jun 29, 2011 at 12:06:29PM +0200, Paolo Bonzini wrote:
On 06/29/2011 12:03 PM, Christoph Hellwig 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.

Agreed, I see a use for multiple queues (MSI-X), but not for
multiple queues shared by a single LUN.

Then let's make it explicit in the spec?

What, forbid it or say ordering is not guaranteed? The latter is already explicit with the wording suggested in the thread.

Paolo



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