Re: [Qemu-devel] [PATCH] net: Change help text to list -netdev instead of -net by default

[Paolo Bonzini]

On 08/05/2015 11:36, Thomas Huth wrote:
> Looking at the output of "qemu-system-xxx -help", you easily get
> the impression that "-net" is the preferred way instead of "-netdev"
> to specify host network interface, since the "-net" option is
> omnipresent but the "-netdev" option is only listed as a one-liner
> at the end. This is ugly since "-net" is considered as legacy and
> even might be removed one day. Thus, this patch switches the output
> to explain the host network interfaces with the "-netdev" option
> instead, moving the legacy "-net" option into some few lines at
> the end.
> 
> Signed-off-by: Thomas Huth <address@hidden>
> ---
>  qemu-options.hx | 66 
> ++++++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 39 insertions(+), 27 deletions(-)

That would be great if it worked for all machine types, but it doesn't.
 For example, there's no equivalent of:

$ qemu-system-arm -net user -net nic -machine versatilepb

You cannot just use -netdev:

$ qemu-system-arm -netdev user,id=nd0 -machine versatilepb
Warning: netdev nd0 has no peer

You cannot use -netdev and -net together:

$ qemu-system-arm -netdev user,id=nd0 -net nic -machine versatilepb
Warning: vlan 0 is not connected to host network
Warning: netdev nd0 has no peer

This particular board has a PCI controller, so you can just add a PCI
NIC using -netdev/-device, but still that wouldn't be a match for "-net
user -net nic" (which puts a smc91c111 NIC on sysbus).  In most embedded
boards there's not even a PCI controller.

So the patch is great, but I wouldn't say it's deprecated, because in
practice it isn't.

Paolo