"Michael S. Tsirkin" <m...@redhat.com> writes:
> On Thu, Feb 25, 2010 at 01:07:54PM +0100, Markus Armbruster wrote:
>> "Michael S. Tsirkin" <m...@redhat.com> writes:
>>
>> > On Thu, Feb 25, 2010 at 11:10:15AM +0100, Markus Armbruster wrote:
>> >> Guest device and host netdev are peers, i.e. it's a 1:1 relation.
>> >> However, we fail to enforce that:
>> >>
>> >> $ qemu -nodefaults --nographic -netdev user,id=net0 -device
>> >> e1000,netdev=net0 -device virtio-net-pci,netdev=net0 -monitor stdio
>> >> QEMU 0.12.50 monitor - type 'help' for more information
>> >> (qemu) info network
>> >> Devices not on any VLAN:
>> >> net0: net=10.0.2.0, restricted=n peer=virtio-net-pci.0
>> >> e1000.0: model=e1000,macaddr=52:54:00:12:34:56 peer=net0
>> >> virtio-net-pci.0: model=virtio-net-pci,macaddr=52:54:00:12:34:57
>> >> peer=net0
>> >>
>> >> It's all downhill from there.
>> >>
>> >> Signed-off-by: Markus Armbruster <arm...@redhat.com>
>> >> ---
>> >> hw/qdev-properties.c | 3 +++
>> >> net.c | 1 +
>> >> 2 files changed, 4 insertions(+), 0 deletions(-)
>> >>
>> >> diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
>> >> index 277ff9e..89efd91 100644
>> >> --- a/hw/qdev-properties.c
>> >> +++ b/hw/qdev-properties.c
>> >> @@ -341,6 +341,9 @@ static int parse_netdev(DeviceState *dev, Property
>> >> *prop, const char *str)
>> >> *ptr = qemu_find_netdev(str);
>> >> if (*ptr == NULL)
>> >> return -1;
>> >> + if ((*ptr)->peer) {
>> >> + return -1;
>> >> + }
>> >
>> > Not even -EBUSY?
>> > Can this produce a helpful diagnostic message?
>>
>> Callers take care of that. It's how property parse methods work.
>> In this case:
>>
>> property "virtio-net-pci.netdev": failed to parse "net0"
>> can't set property "netdev" to "net0" for "virtio-net-pci"
>
> Yes, but does not tell you why. If parse_netdev even just returned a
> meaningful
> error code, we could see:
> can't set property "netdev" to "net0" for "virtio-net-pci":
> device or resource busy.
>
> which is at least a hint that something else uses it.
>
> As it is, it looks like qemu could not parse "net0"
> which is not really right.
Gerd, what do you think about changing the contract for property parse
methods to return -EINVAL, -EBUSY and such?
