Re: [libvirt] [PATCH v1 17/19] tests: Introduce basic vhost-scsi test

On Tue, Aug 09, 2016 at 10:44:44AM -0400, Eric Farman wrote: > > On 08/09/2016 08:22 AM, Daniel P. Berrange wrote: >>>> + <hostdev mode='subsystem' type='scsi'> >>>> + <source protocol='vhost' wwpn='naa.5123456789abcde0'/> >>>> + </hostdev> >> I'm not sure this syntax really makes sense. >> >> IIRC, currently <hostdev type="scsi"> is used to passthrough an individual >> SCSI LUNs from the host to the guest. >> >> With vhost-scsi, IIUC, you are passing through an entire (virtual) SCSI HBA >> to the guest. So I think it better for us to not reuse type="scsi" for that >> purpose. Instead it feels like we should be adding a type="scsi_host" for >> passthrough of entire HBAs > Would that cause confusion amongst an existing type='scsi' hostdev, since a > "scsi_hostX" turns up in the source tag? Example from the libvirt doc: > > <devices> > <hostdev mode='subsystem' type='scsi' sgio='filtered' rawio='yes'> > <source> > <adapter name='scsi_host0'/> > <address bus='0' target='0' unit='0'/> > </source> > <readonly/> > <address type='drive' controller='0' bus='0' target='0' unit='0'/> > </hostdev> > </devices> > > > Could make it be "type='vhost_scsi'" or something else, if that clarifies > things. No, it should be type=scsi_host, so that in the future if we want to pass through entire SCSI or iSCSI HBAs without vhost-scsi, then we can do it.

> (Question from my own ignorance; does an iSCSI target with more than one LUN > behind it get rejected if specified here, instead of using a <pool> tag?) The IQN name has to include the LUN in it - if that's left out, QEMU would complain that no LUN was specified.

>> Obviously this has major implications for almost all patches in this series > Splitting this out as a new hostdev type would mean it's not being > shoehorned into the existing SCSI parts. That would probably make the > entire series less unwieldy by dropping the separate protocol that exists > herein. Regards, Daniel