"Michael S. Tsirkin" <m...@redhat.com> writes: > On Wed, Sep 25, 2013 at 10:14:49AM +0000, Zhanghaoyu (A) wrote: >> >> >> >> Hi, all >> >> >> >> >> >> >> >> Do live migration if emulated NIC's MAC has been changed, RARP >> >> >> >> with wrong MAC address will broadcast via >> >> >> >> qemu_announce_self in destination, so, long time network >> >> >> >> disconnection probably happen. >> >> >> > >> >> >> >Good catch. >> >> >> > >> >> >> >> I want to do below works to resolve this problem, 1. change >> >> >> >> NICConf's MAC as soon as emulated NIC's MAC changed in guest >> >> >> > >> >> >> >This will make it impossible to revert it correctly on reset, won't >> >> >> >it? >> >> >> > >> >> >> You are right. >> >> >> virsh reboot <domain>, or virsh reset <domain>, or reboot VM >> >> >> from guest, will revert emulated NIC's MAC to original one >> >> >> maintained in NICConf. >> >> >> During the reboot/reset flow in qemu, emulated NIC's reset handler >> >> >> will sync the MAC address in NICConf to the MAC address in >> >> >> emulated NIC structure, e.g., virtio_net_reset sync the MAC >> >> >> address in NICConf to VirtIONet'mac. >> >> >> >> >> >> BTW, in native scenario, reboot will revert the changed MAC to >> >> >> original one, too. >> >> >> >> >> >> >> 2. sync NIC's (more precisely, queue) MAC to corresponding >> >> >> >> NICConf in NIC's migration load handler >> >> >> >> >> >> >> >> Any better ideas? >> >> >> >> >> >> >> >> Thanks, >> >> >> >> Zhang Haoyu >> >> >> > >> >> >> >I think announce needs to poke at the current MAC instead of >> >> >> > the default one in NICConf. >> >> >> >We can make it respect link down state while we are at it. >> >> >> > >> >> >> NICConf structures are incorporated in different emulated NIC's >> >> >> structure, e.g., VirtIONet, E1000State_st, RTL8139State, etc., >> >> >> since so many kinds of emulated NICs, they are described by >> >> >> different structures, how to find all NICs' current MAC? >> >> >> >> >> >> Maybe we can introduce a pointer member 'current_mac' to NICConf >> >> >> structure, which points to the current MAC, then we can find >> >> >> all current MACs from NICConf.current_mac. >> >> > >> >> >I wouldn't make it a pointer, just a buffer with the mac, copy it there. >> >> >Maybe call it "softmac" that's what it is really. >> >> > >> >> >> Can we broadcast the RARP with current MAC in NIC's migration >> >> >> load handler respectively? >> >> >> >> >> >> Thanks, >> >> >> Zhang Haoyu >> >> > >> >> >It's not so simple, you need to retry several times. >> >> > >> >> Could you make a statement for 'retry several times' ? >> >> Is it the process of retrying several times to sending RARP in >> >> qemu_announce_self_once? >> > >> >yes >> > >> >> 'broadcast the RARP with current MAC in NIC's migration load handler >> >> respectively' is distributing the job of what qemu_announce_self >> >> does to every NIC's migration load handler, e.g., in virtio NIC's >> >> migration load handler virtio_net_load, we can create a timer to >> >> retry several times to send ARAP with current MAC for this NIC, >> >> just as same as qemu_announce_self does. >> > >> >I don't see a lot of value in this yet. >> > >> In my opinion, it's not so good to introduce a 'softmac' member to >> NICConf, which is not essential function of NICConf. > > Maybe not essential but 100% of hardware we emulate supports softmacs.
Yes, but NICConf is about NIC *configuration*, not random common NIC state. We can capture common NIC state in a separate, properly named data type. If we want to bunch it together with common configuration in NICConf instead, then better rename NICConf to something that actually reflects its changed purpose. I doubt this would be a good idea. >> And, distributing the job of what qemu_announce_self does to every >> NIC's migration load handler has no disadvantages over >> qemu_announce_self, > > I see some disadvantages, yes. > You are going to add code to all devices instead of > doing it in one place, there better be a good reason for this. Keeping code common to many (most?) NICs factored out makes sense. We've started doing that for block devices, in hw/block/block.c. So far, the only code there is about configuration, thus we work with BlockConf. [...]