When starting a VM with a vhost-user interface in server mode qemu will
wait for the incoming connection without running CPUs. This isn't really
documented in our XML. Additionally when hotplugging the same interface
the above will not happen.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
---
 docs/formatdomain.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 4a5241e610..8ab6b7282d 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -6346,6 +6346,11 @@ two attributes ``enabled`` (which accepts ``yes`` and ``no``) and
 ``timeout`` which specifies the amount of seconds after which
 hypervisor tries to reconnect.

+Note that when ``mode='server'`` is used, the hypervisor will wait for the
+incomming connection to be established prior to actually running the VM. This is
+not possible when hotplugging an interface the same config so the VM will
+continue to run even when no connection is made. It's advised to use
+``mode='client'`` instead.

 vhost-user connection with passt backend
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-- 
2.48.1

On a Thursday in 2025, Peter Krempa wrote:
>When starting a VM with a vhost-user interface in server mode qemu will
>wait for the incoming connection without running CPUs. This isn't really
>documented in our XML. Additionally when hotplugging the same interface
>the above will not happen.
>
>Signed-off-by: Peter Krempa <pkrempa@redhat.com>
>---
> docs/formatdomain.rst | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
>index 4a5241e610..8ab6b7282d 100644
>--- a/docs/formatdomain.rst
>+++ b/docs/formatdomain.rst
>@@ -6346,6 +6346,11 @@ two attributes ``enabled`` (which accepts ``yes`` and ``no``) and
> ``timeout`` which specifies the amount of seconds after which
> hypervisor tries to reconnect.
>
>+Note that when ``mode='server'`` is used, the hypervisor will wait for the
>+incomming connection to be established prior to actually running the VM. This is

*incoming

>+not possible when hotplugging an interface the same config so the VM will

I can't parse this sentence.

an interface with the same config?

>+continue to run even when no connection is made. It's advised to use
>+``mode='client'`` instead.
>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

Jano

On Thu, Feb 20, 2025 at 11:13:19 +0100, Ján Tomko wrote:
> On a Thursday in 2025, Peter Krempa wrote:
> > When starting a VM with a vhost-user interface in server mode qemu will
> > wait for the incoming connection without running CPUs. This isn't really
> > documented in our XML. Additionally when hotplugging the same interface
> > the above will not happen.
> > 
> > Signed-off-by: Peter Krempa <pkrempa@redhat.com>
> > ---
> > docs/formatdomain.rst | 5 +++++
> > 1 file changed, 5 insertions(+)
> > 
> > diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
> > index 4a5241e610..8ab6b7282d 100644
> > --- a/docs/formatdomain.rst
> > +++ b/docs/formatdomain.rst
> > @@ -6346,6 +6346,11 @@ two attributes ``enabled`` (which accepts ``yes`` and ``no``) and
> > ``timeout`` which specifies the amount of seconds after which
> > hypervisor tries to reconnect.
> > 
> > +Note that when ``mode='server'`` is used, the hypervisor will wait for the
> > +incomming connection to be established prior to actually running the VM. This is
> 
> *incoming
> 
> > +not possible when hotplugging an interface the same config so the VM will
> 
> I can't parse this sentence.
> 
> an interface with the same config?

I've changed it to:

This is not possible when hotplugging an interface with such config ...

> 
> > +continue to run even when no connection is made. It's advised to use
> > +``mode='client'`` instead.
> > 
> 
> Reviewed-by: Ján Tomko <jtomko@redhat.com>
> 
> Jano