Re: [Qemu-devel] [PATCH V7 0/5] Send the gratuitous by guest

[Jason Wang]

On 03/07/2013 06:04 PM, Michael S. Tsirkin wrote:
> On Thu, Mar 07, 2013 at 04:23:46PM +0800, Jason Wang wrote:
>> This series tries to let guest instead of qemu to send the gratuitous packets
>> after migration when guest is capable of doing this. This is needed since 
>> it's
>> impossible for qemu to keep track of all configurations (e.g 802.1Q) and mac
>> addresses (more than one mac address may be used by guest). So qemu can't 
>> build
>> gratuitous packets for all those configurations properly. The only solution 
>> is
>> let guest driver who knew all needed information to do this.
>>
>> The series first introduces a new runstate which just tracks the state when 
>> the
>> migration is finished and guest is about to start. And then we can just 
>> trying
>> to notify the guest to send the GARP after changing from this state to
>> running. A model specific announcing method were also also introduced to let
>> each kinds of nic do its own notification. When there's no such method 
>> register
>> for the nic, the old style of sending RARP were kept. And the last two 
>> patches
>> implemented the virtio-net method of notification.
> Do we want to retry SELF_ANNOUNCE_ROUNDS?

Yes, we do the announcement several times like in the past.
>> Changes from V6:
>> - introduce a new runstate instead of using a global variable check the state
>>
>> Changes from V5:
>> - use a global variable to decide whether an announcement is needed after 
>> migration
>> - align with virtio spec and let guest ack the announcement notification 
>> through
>>   control vq instead of config status writing
>>
>> Changes from V4:
>> - keep the old behavior that send the gratuitous packets only after migration
> I wonder why it's a sane thing to do. How about simply sending the event 
> after load?

The aim is to limit the change of the behaviour to focus on migration.

We may also need this after cont, and then maybe we can just do this
unconditionally in vm_start().
>> - decide whether to send gratuitous packets by previous runstate instead of 
>> a dedicated parameter
>> - check virtio_net_started() instead of VIRTIO_NET_S_LINK_UP before issue 
>> the config update interrupt
>> - move VIRTIO_NET_S_ANNOUNCE to 0x100 and supress guest config write to RO 
>> bits
>> - cleanups suggested by Michael
>>
>> Tested with migration within 802.1Q.
>>
>> Jason Wang (5):
>>   runstate: introduce prelaunch-migrate state
>>   net: announce self after vm is started
>>   net: model specific announcing support
>>   virtio-net: notify guest to annouce itself
>>   virtio-net: compat guest announce
>>
>>  hw/pc.h           |    6 +++++-
>>  hw/virtio-net.c   |   30 ++++++++++++++++++++++++++++++
>>  hw/virtio-net.h   |   15 ++++++++++++++-
>>  include/net/net.h |    2 ++
>>  migration.c       |    4 +---
>>  qapi-schema.json  |    5 ++++-
>>  savevm.c          |    8 ++++++--
>>  vl.c              |    8 +++++++-
>>  8 files changed, 69 insertions(+), 9 deletions(-)