Hi Laine,
The <source dev/> setting will be ignored after "virsh define" or when you
save after "virsh edit".
Do you think it is a bug?
Details:
SC1: define
# cat rhel.xml | grep /interface -B6
<interface type='vhostuser'>
<mac address='52:54:00:e2:ba:2c'/>
<model type='virtio'/>
<backend type='passt'/>
<source dev='eno8303'/>
<address type='pci' domain='0x0000' bus='0x01' slot='0x00'
function='0x0'/>
</interface>
# virsh define rhel.xml
Domain 'rhel' defined from rhel.xml
# virsh dumpxml rhel --xpath //interface
<interface type="vhostuser">
<mac address="52:54:00:e2:ba:2c"/>
<model type="virtio"/>
<backend type="passt"/>
<address type="pci" domain="0x0000" bus="0x01" slot="0x00"
function="0x0"/>
</interface>
SC2: virsh edit
# virsh edit rhel
<interface type='vhostuser'>
<mac address='52:54:00:e2:ba:2c'/>
<model type='virtio'/>
<backend type='passt'/>
<source dev='eno8303'/>
<portForward proto='tcp' address='10.73.211.16' dev='eno8303'>
<range start='2000'/>
<range start='3000' to='3001'/>
</portForward>
<address type='pci' domain='0x0000' bus='0x01' slot='0x00'
function='0x0'/>
</interface>
after save, check the xml:
# virsh dumpxml rhel --xpath //interface
<interface type="vhostuser">
<mac address="52:54:00:e2:ba:2c"/>
<portForward proto="tcp" address="10.73.211.16" dev="eno8303">
<range start="2000"/>
<range start="3000" to="3001"/>
</portForward>
<model type="virtio"/>
<backend type="passt"/>
<alias name="net0"/>
<address type="pci" domain="0x0000" bus="0x01" slot="0x00"
function="0x0"/>
</interface>
start the vm, check the process:
qemu 28692 0.0 0.0 205640 25788 ? Ss 21:07 0:00 passt
--vhost-user --one-off --socket /run/libvirt/qemu/passt/1-rhel-net0.socket
--pid /run/libvirt/qemu/passt/1-rhel-net0-passt.pid --tcp-ports
10.73.211.16%eno8303/2000,3000:3001
BR,
Yalan
On Thu, Mar 6, 2025 at 5:50 AM Laine Stump <la...@laine.org> wrote:
> Just now took my daily look at the list and saw this patch...
>
> On 3/5/25 11:42 AM, Ján Tomko wrote:
> > On a Wednesday in 2025, Yalan Zhang wrote:
> >> Fix a typo and update the setting in the example. The documentation
> >> explains that "when passt is the backend,...the ``<source>``
> >> path/type/mode are all implied to be "matching the passt process"
> >> so **must not** be specified." Additionally, this source dev setting is
> >> ignored in practice. Therefore, let's remove it from the example to
> >> avoid any
> >> confusion.
> >>
> >> Signed-off-by: Yalan Zhang <yalzh...@redhat.com>
> >> ---
> >> docs/formatdomain.rst | 3 +--
> >> 1 file changed, 1 insertion(+), 2 deletions(-)
> >>
> >> diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
> >> index cbe378e61d..e84e0a0e8e 100644
> >> --- a/docs/formatdomain.rst
> >> +++ b/docs/formatdomain.rst
> >> @@ -5154,7 +5154,7 @@ destined for the host toward the guest instead),
> >> and a socket between
> >> passt and QEMU forwards that traffic on to the guest (and back out,
> >> of course).
> >>
> >
> > Oops, I have not looked at how this renders when reviewing the original
> > patch - that the extra characters prevent the :since: tag from working.
> >
> >> -*(:since:`Since 11.1.0 (QEMU and KVM only)` you may prefer to use the
> >> +:since:`Since 11.1.0 (QEMU and KVM only)` you may prefer to use the
> >> passt backend with the more efficient and performant type='vhostuser'
> >> rather than type='user'. All the options related to passt in the
> >> paragraphs below here also apply when using the passt backend with
> >
> > Additional context:
> > type='vhostuser'; any other details specific to vhostuser are
> > described* `here
> > <formatdomain.html#vhost-user-connection-with-passt-backend>`__.)
> >
> > So the asterisk ending the italics and the ending parenthesis should be
> > removed too.
>
> Yeah, sorry I didn't notice that the italicization not only didn't work,
> but also prevented the :since: tag from working. That's unfortunate - I
> would have preferred for that paragraph to be italicized :-/
>
> >
> > I can squash that change in before pushing, unless someone objects
> > to removing the italics and parenthesis.
> >
> >> @@ -6378,7 +6378,6 @@ setting guest-side IP addresses with ``<ip>``
> >> and port forwarding with
> >> <interface type='vhostuser'>
> >> <backend type='passt'/>
> >> <mac address='52:54:00:3b:83:1a'/>
> >> - <source dev='enp1s0'/>
>
>
> It is correct the path/type/mode in <source> are not used or allowed for
> type='vhostuser', but that's not what is being set in this example - it
> is setting source dev, which *is* valid to set - for both flavors of
> passt connection the source dev is the name of the host network device
> passt uses when figuring out what default route to provide to the guest
> in its DHCP responses (and also what IP address and netmask to provide
> by default in the DHCP response when specific IP/netmask aren't set).
>
> So this line should remain in the example. Please don't remove it.
>
>
>
> >> <ip address='10.30.0.5 prefix='24'/>
> >> </interface>
> >> </devices>
> >> --
> >
> > Reviewed-by: Ján Tomko <jto...@redhat.com>
>
> >
> > Jano
>
>
