[libvirt] [PATCH v3 0/5] introduce support for an embedded driver mode

[Daniel P. Berrangé]

On Thu, Jan 09, 2020 at 05:22:39PM +0100, Michal Privoznik wrote:
> On 1/9/20 2:15 PM, Daniel P. Berrangé wrote:
> > On Wed, Jan 08, 2020 at 05:30:23PM +0100, Michal Privoznik wrote:
> > > On 12/20/19 3:16 PM, Daniel P. Berrangé wrote:
> > > > 
> > > 
> > > Hm.. maybe I'm doing something wrong, but the following doesn't work for me.
> > > Note, "fedora" is a VM with two disks:
> > > 
> > >      <disk type='file' device='disk'>
> > >        <driver name='qemu' type='qcow2' discard='unmap'/>
> > >        <source file='/var/lib/libvirt/images/fedora.qcow2'/>
> > >        <target dev='sda' bus='scsi'/>
> > >        <boot order='1'/>
> > >        <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> > >      </disk>
> > >      <disk type='network' device='disk'>
> > >        <driver name='qemu' type='raw'/>
> > >        <source protocol='iscsi'
> > > name='iqn.2017-03.com.mprivozn:server-lun-0/0'>
> > >          <host name='iscsi-server.example.com' port='3260'/>
> > >          <initiator>
> > >            <iqn name='iqn.2017-03.com.mprivozn:client'/>
> > >          </initiator>
> > >          <auth username='mprivozn'>
> > >            <secret type='iscsi' usage='iscsi-secret-pool'/>
> > >          </auth>
> > >        </source>
> > >        <target dev='vda' bus='virtio'/>
> > >        <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
> > > function='0x0'/>
> > >      </disk>
> > > 
> > > 
> > > libvirt.git/_build # ./tools/virsh -c qemu:///embed?root=/tmp/embed/
> > > Welcome to virsh, the virtualization interactive terminal.
> > > 
> > > Type:  'help' for help with commands
> > >         'quit' to quit
> > > 
> > > virsh # list --all
> > >   Id   Name     State
> > > -------------------------
> > >   -    fedora   shut off
> > > 
> > > virsh # connect secret:///embed?root=/tmp/embed
> > 
> > Ok, you're opening the secret driver in embedded mode
> > 
> > If you *also* open the QEMU driver now, it will use
> > this embedded secret driver directly.
> > 
> > > 
> > > virsh # secret-list
> > >   UUID                                   Usage
> > > -----------------------------------------------------------------
> > >   4cf62bac-6a9f-4b9a-ba33-8c4d96b0e2e4   iscsi iscsi-secret-pool
> > 
> > I guess you created the XML file for this secrete previously ?
> > 
> > 
> > > virsh # connect qemu:///embed?root=/tmp/embed
> > 
> > Note that this now *closes* the existing connection, so the
> > embeded secret driver is now closed, and QEMU will speak to
> > libvirtd (or virtsecretd) for secrets now.
> > 
> > Basically virsh is not a suitable tool for using the
> > drivers in embedded mode since it is only capable of
> > opening a single driver connection at a time.
> > 
> > > virsh # start fedora
> > > 2020-01-08 15:37:57.294+0000: 44566: info : libvirt version: 6.0.0
> > > 2020-01-08 15:37:57.294+0000: 44566: info : hostname: moe
> > > 2020-01-08 15:37:57.294+0000: 44566: warning : qemuDomainDefValidate:5835 :
> > > CPU topology doesn't match numa CPU count; partial NUMA mapping is obsoleted
> > > and will be removed in future
> > > error: Failed to start domain fedora
> > > error: internal error: URI must be secret:///embed
> > 
> > Oh, that's odd - it seems to be trying to access the embedded
> > secret driver but failing a URI sanity check. This is probably
> > a result of you previously opening & then closing the embedded
> > secret driver. This is not really a supported use case anyway.
> 
> 
> Okay, since your program works, you have my:
> 
> Reviewed-by: Michal Privoznik <mprivozn at redhat.com>
> 
> for the series. However, as I suggested on the list, we should tell users
> explicitly that this feature is still under development and we may not be
> able to guarantee full backwards compatibility. May be worth putting
> somewhere into news.xml ;-)

The docs in the QEMU patch do mention twice that this is experimental



Regards,
Daniel
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