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Re: [libvirt] [PATCH 0/2] qemu: add new disk type='lun' for bus='virtio'

On 12/23/2011 01:42 AM, Paolo Bonzini wrote:
> On 12/23/2011 12:15 AM, Daniel P. Berrange wrote:
>> The 'type' attribute refers to how the host emulator deals with the
>> disk.
>> The 'device' attribute refers to what type of device hardware is exposed
>> to the guest.
>> What we're doing here is controlling whether the host emulator allows
>> SG_IO. The guest visible device hardware has not changed at all. Thus
>> using the 'type' attribute is the correct approach.
> You could also say that the host is still accessing the device in the
> same way (via /dev/sdX).  The guest visible device changes because in
> one case it allows SG_IO, in the other it doesn't, even if the host
> device is the same.

I also tend to agree that 1) this is a guest-visible change in behavior
for the same host resource, and 2) Paolo's proposals for virtio-scsi LUN
pass-through present device='lun'.

Or do we mix the two concepts?  That is, type='lun' is used to control
SG_IO enabling, while device='lun' is used to control LUN pass-through,
and you can even have the combination type='lun' device='lun'?

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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