[libvirt] SCSI command passthrough

[Dor Laor]

On 09/06/2012 07:51 PM, Geert Jansen wrote:
> Hi,
>
> i'm trying to pass through SCSI commands from a guest to a host. Both
> guest and host are RHEL 6.3. The relevant section in my XML is:
>
>    <devices>
>      <disk type='block' device='lun'>
>        <driver name='qemu' type='raw' cache='none'/>
>        <source dev='/dev/sdb'/>
>        <target dev='sdb' bus='scsi'/>
>        <address type='drive' controller='0' bus='0' target='1' unit='0'/>
>      </disk>
>      <controller type='scsi' index='0' model='virtio-scsi'>
>        <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
> function='0x0'/>
>      </controller>
>    ...
>    </devices>
>
> Commands that are whitelisted by the host kernel come through (e.g.
> "sg_inq"), but other commands don't (e.g. "sg_persist").
>
> I need sg_persist so i tried making qemu-kvm setuid root. This works.
>
> Is there a better way to allow arbitrary SCSI commands, perferably on a
> per-VM basis, rather than making qemu setuid root?

There is Paolo's suggestion to add cgroup filtering for sg_io:
http://lwn.net/Articles/501742/

But it might had scared people as it got no response. Paolo, would you 
give it another shot?

Cheers,
Dor

>
> Regards,
> Geert
>
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