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[Qemu-devel] Re: future of the virtio-blk serial number support


From: Anthony Liguori
Subject: [Qemu-devel] Re: future of the virtio-blk serial number support
Date: Thu, 28 Jan 2010 08:09:00 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Lightning/1.0pre Thunderbird/3.0

On 01/28/2010 06:43 AM, Christoph Hellwig wrote:
Back iSeptember 2007 Michael made the serial number support in qemu
optional and off by default, and in October 2009 Rusty reverted the
Linux virtio-blk support for it.  Given that I can't find support in
any other virtio implementation that makes the feature look essentially
dead.

How should we proceed with adding more fields to struct virtio_blk_config?
I would suggest removing the identity field, declaring
VIRTIO_BLK_F_IDENTIFY officially deprecated and adding the new fields
directly after blk_size again, maybe with a comment that these new
features can't be advertized together with VIRTIO_BLK_F_IDENTIFY.

I need to add a new optiomal_io_size field soon to support the block
topology information when using virtio which is quite important when
using RAID arrays as backend, and I'd prefer to do it in a way that's
compatibly with the PCI spec.

Sounds good to me. IDENTIFY is basically impossible to implement in it's current form with virtio-pci.

We should put something in the spec mentioning that config space is limited and large values should not be placed in it. Instead, implementations should use a control ring queue to pass large data sets.

Regards,

Anthony Liguori




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