On 22/07/2015 13:46, Daniel P. Berrange wrote:
IIUC, the SCSI passthrough feature for virtio-blk is enabled by
setting the 'scsi=on' property on the virtio-blk device, which is
exposed by libvirt with XML:
<disk type='block' device='lun'>
<driver name='qemu' type='raw'/>
<source dev='/dev/sda'/>
<target dev='vda' bus='virtio'/>
</disk>
(For use with virtio-scsi you'd just change the <target> element)
So if the guest is using virtio-1.0, then this will now fail to boot, or
cause an error from monitor hotplug. This is not too bad, but I'm just
wondering if there's anything else we ought to think about doing in libvirt
in this situation. Normally we'd try to detect unsupported things upfront
so we can report VIR_ERR_CONFIG_UNSUPPORTED, instead of the generic error
code VIR_ERR_INTERNAL_ERROR, but perhaps this is sufficiently niche to
not worry about it and its fine to just delegate error reporting to QEMU ?
Probably. Note that it will be a long time before the default is
changed to 1.0 (if it ever will). Perhaps you can start warning now
about <disk type='block' device='lun'>, and suggest using
virtio-scsi
instead?
Paolo