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From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 30 Sep 2009 21:30:32 +0930
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Subject: [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config
	breakage
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: john cooper <john.cooper@third-harmonic.com>, "Michael S. Tsirkin" <mst@redhat.com>, john cooper <john.cooper@redhat.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>, jens.axboe@oracle.com, Vadim Rozenfeld <vrozenfe@redhat.com>

On Wed, 30 Sep 2009 11:47:00 am Anthony Liguori wrote:
> Rusty Russell wrote:
> > On Wed, 30 Sep 2009 06:25:39 am Anthony Liguori wrote:
> >   
> >> virtio-blk isn't an ATA device so why pretend like it is?
... 
> That's an argument to implement the HDIO_GET_IDENTITY ioctl in the Linux 
> virtio-blk driver.  That's a totally reasonable thing to do.

Your second sentence contradicts your first here.  If it's reasonable to
imitate ATA in Linux, it's reasonable to imitate ATA in virtio.

Using an existing standard should always be the default; one should need a
compelling reason *not* to do so.  In practice, (1) that code already exists
in kvm, and (2) it makes the Linux implementation trivial.

So, what are the real arguments?
(1) Some fields are redundant (eg. geometry) with existing fields already.
(2) Future fields will have to decide whether to use ATA IDENTIFY or normal
    features,
(3) We don't know enough about ATA IDENTIFY to do a decent job of filling
    it in.

I can buy (1), but I still have to deal with (2) and (3) if they're inside
the virtio_blk driver anyway.

Anything else?
Rusty.