[libvirt] [libvirt PATCH v2 09/44] Remove qemuDomainSupportsNetdev

[Andrea Bolognani]

On Mon, 2018-04-09 at 17:20 +0200, Ján Tomko wrote:
> Now that we assume QEMU_CAPS_NETDEV, the only thing left to check
> is whether we need to use the legacy -net syntax because of
> a non-conforming armchitecture.

I see you're having "pun" writing these commit messages ;)

[...]
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 05cc4903a4..4e8c4a7bd4 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -8217,7 +8217,7 @@ qemuBuildVhostuserCommandLine(virQEMUDriverPtr driver,
>      unsigned int queues = net->driver.virtio.queues;
>      char *nic = NULL;
>  
> -    if (!qemuDomainSupportsNetdev(def, qemuCaps, net)) {
> +    if (!qemuDomainSupportsNicdev(def, net)) {
>          virReportError(VIR_ERR_INTERNAL_ERROR,
>                         "%s", _("Netdev support unavailable"));

With the change, this error message becomes misleading: it's not
that -netdev support is unavailable, it's just that -device can't
be used for the NIC and we can't (won't?) use -netdev without it.

I guess you can just s/Netdev/nicdev/ and call it a day, it's not
like it makes the error message any harder, or easier, to grasp.

> @@ -8552,23 +8552,14 @@ qemuBuildInterfaceCommandLine(virQEMUDriverPtr driver,
>              goto cleanup;
>      }
>  
> -    /* Possible combinations:
> -     *
> -     *  1. Old way:   -net nic,model=e1000,vlan=1 -net tap,vlan=1
> -     *  2. Semi-new:  -device e1000,vlan=1        -net tap,vlan=1
> -     *  3. Best way:  -netdev type=tap,id=netdev1 -device e1000,id=netdev1
> -     *
> -     * NB, no support for -netdev without use of -device
> -     */

I think you should leave the comment in, because most of it still
applies even in our brave new, legacy-free world.

Basically all you should do is drop option 2, and (optionally)
rework option 3 a little. The result could look like

  * Old way: -net nic,model=e1000,vlan=1 -net tap,vlan=1
  * New way: -device e1000,id=netdev1    -netdev type=tap,id=netdev1

I suggest reworking the "new way" line because I think having the
guest part and host part listed in the same order both times makes
the whole thing easier to understand.

> -    if (qemuDomainSupportsNetdev(def, qemuCaps, net)) {
> +    if (qemuDomainSupportsNicdev(def, net)) {
>          if (!(host = qemuBuildHostNetStr(net, driver,
>                                           ',', vlan,
>                                           tapfdName, tapfdSize,
>                                           vhostfdName, vhostfdSize)))
>              goto cleanup;
>          virCommandAddArgList(cmd, "-netdev", host, NULL);
> -    }
> -    if (qemuDomainSupportsNicdev(def, net)) {
> +
>          if (!(nic = qemuBuildNicDevStr(def, net, vlan, bootindex,
>                                         vhostfdSize, qemuCaps)))
>              goto cleanup;
> @@ -8577,8 +8568,7 @@ qemuBuildInterfaceCommandLine(virQEMUDriverPtr driver,
>          if (!(nic = qemuBuildNicStr(net, "nic,", vlan)))
>              goto cleanup;
>          virCommandAddArgList(cmd, "-net", nic, NULL);
> -    }
> -    if (!qemuDomainSupportsNetdev(def, qemuCaps, net)) {
> +
>          if (!(host = qemuBuildHostNetStr(net, driver,
>                                           ',', vlan,
>                                           tapfdName, tapfdSize,

Incidentally, this makes the flow of the function much easier to
follow. Nice!

> @@ -8658,7 +8648,7 @@ qemuBuildNetCommandLine(virQEMUDriverPtr driver,
>              int vlan;
>  
>              /* VLANs are not used with -netdev, so don't record them */
> -            if (qemuDomainSupportsNetdev(def, qemuCaps, net))
> +            if (qemuDomainSupportsNicdev(def, net))
>                  vlan = -1;
>              else
>                  vlan = i;

Again, you probably want to mention that -netdev requires -device,
so that the comment won't look completely out of place or require
developers to be intimately aware of how the two work together.

[...]
> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index c145c42bcd..8aacd8376f 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c
> @@ -956,7 +956,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
>          queueSize = net->driver.virtio.queues;
>          if (!queueSize)
>              queueSize = 1;
> -        if (!qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) {
> +        if (!qemuDomainSupportsNicdev(vm->def, net)) {
>              virReportError(VIR_ERR_INTERNAL_ERROR,
>                             "%s", _("Netdev support unavailable"));
>              goto cleanup;

Same as the first instance.

> diff --git a/src/qemu/qemu_interface.c b/src/qemu/qemu_interface.c
> index cebb490221..24c0174bf9 100644
> --- a/src/qemu/qemu_interface.c
> +++ b/src/qemu/qemu_interface.c
> @@ -646,7 +646,7 @@ qemuInterfaceOpenVhostNet(virDomainDefPtr def,
>       * option), don't try to open the device.
>       */
>      if (!(virQEMUCapsGet(qemuCaps, QEMU_CAPS_VHOST_NET) &&
> -          qemuDomainSupportsNetdev(def, qemuCaps, net))) {
> +          qemuDomainSupportsNicdev(def, net))) {
>          if (net->driver.virtio.name == VIR_DOMAIN_NET_BACKEND_TYPE_VHOST) {
>              virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>                             "%s", _("vhost-net is not supported with "

The full comment, only half of which is contained in the hunk, is

  If qemu doesn't support vhost-net mode (including the -netdev
  command option), don't try to open the device.

Once again, it should point to -device rather than -netdev.


Trusting that you'll tweak both comments and error messages so that
they will not confuse the next soul wandering through these lands,

  Reviewed-by: Andrea Bolognani <abologna at redhat.com>

-- 
Andrea Bolognani / Red Hat / Virtualization