[libvirt PATCH 3/6] docs: introduces new vhostuser disk type

[Peter Krempa]

On Tue, Feb 02, 2021 at 16:04:09 +0100, Pavel Hrdina wrote:
>      <disk type='vhostuser' device='disk'>
>        <driver name='qemu' type='raw'/>
>        <source type='unix' path='/tmp/vhost-blk.sock' mode='client'>
>          <reconnect enabled='yes' timeout='10'/>
>        </source>
>        <target dev='vda' bus='virtio'/>
>      </disk>
> 
> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
>  docs/formatdomain.rst         | 32 ++++++++++++++++++++++++++++++--
>  docs/schemas/domaincommon.rng | 19 +++++++++++++++++++
>  2 files changed, 49 insertions(+), 2 deletions(-)

[...]

> @@ -2581,6 +2588,18 @@ paravirtualized driver is specified via the ``disk`` element.
>        is not involved (compared to passing say ``/dev/nvme0n1`` via
>        ``<disk type='block'>`` and therefore lower latencies can be achieved.
>  
> +   ``vhostuser``
> +      Enables the hypervisor to connect to another process using vhost-user
> +      protocol. Requires shared memory configured for the VM, for more details
> +      see ``access`` mode for `memoryBacking <#elementsMemoryBacking>` element.

Here we are missing a lot of the caveats of a vhostuser backed disk. A
blanked disclaimer such as:

"Note that the vhost server replaces both the disk frontend and backend
thus almost all of the disk properties can't be configured via the
<disk> XML for this disk type. Additionally features such as blockjobs,
incremental backups and snapshots are not supported for this disk type."

Should do it.