Re: [libvirt] [PATCHv2 4/4] qemu: Implement shared memory device hot-unplug

On 12/17/2015 08:26 PM, John Ferlan wrote: > > On 12/16/2015 09:43 PM, lhuang wrote: >> >> On 12/15/2015 08:39 PM, John Ferlan wrote: >>> [...] >>> >>>>>> + if (rc < 0) >>>>>> + return -1; >>>>>> + >>>>> I know this is a copy of the RemoveRNGDevice; however, this code >>>>> doesn't >>>>> remove an 'obj'. In fact, if !shmem->server.enabled, then we don't >>>>> enter >>>>> the monitor at all. >>>>> >>>>> Thus the following event probably won't happen... >>>> I am not sure what your mean is ... i guess your mean the device >>>> remove >>>> event we get from qmp monitor won't happen ? we will get that >>>> event if >>>> qemu remove shmem device success, it should always happen if qemu >>>> really >>>> remove it and there is no bugs on qemu :) >>>> >>> While reviewing I got lazy and didn't check the non hotplug case to >>> how >>> shmem is added to the vm, but the point I was trying to make is >>> that "if >>> (shmem->server.enabled)" fails (e.g. is false), then there is no "rc = >>> qemuMonitorDelObject(priv->mon, objAlias);" call in this API >>> (similar to >>> RNG code), thus how does the following event get triggered? Even if >>> the >>> condition was true, does detaching the char dev cause the event to be >>> triggered? >>> I thought the event was related to the DelObject code, but I didn't go >>> follow that code >> Oh, i see, event is not related to the object delete, i guess you have >> checked the code and know how it works now ;-) > Maybe you misunderstood - maybe I misunderstood your response... I > didn't go searching through the code, but something just didn't seem > right when looking so I wanted to note it. Looks like i misunderstood :) > Since I figured your model was RNG my thought process was how does RNG > do it and what is different... > > AttachRNG has 3 steps AttachCharDev, AddObject, and AddDevice > DetachRNG has 1 step DelDevice > RemoveRNG has 2 steps DelObject and DetachCharDev > > > AttachShmem has 2 steps AttachCharDev and AddDevice > DetachShmem has 1 step DelDevice > RemoveShmem has 1 step DetachCharDev > > I think my concern was more related to the difference where an RNG has > an Object that gets removed, but Shmem doesn't. ivshmem device doesn't have a QOM object, so no need to add/del a QOM object. and you can check this doc: http://wiki.qemu.org/TexiDemo and see "Inter-VM Shared Memory device" part

> After closer inspection now it seems that this event generation needs to > stay. The RemoveShmem code is generating the event not waiting on it > which perhaps is where my thoughts were when I first went through the > changes. yes, virDomainEventDeviceRemovedNewFromObj() is generating a event and it can trigger the callback functions which registered in qemu driver. Thanks for your help and reply Luayo > John > >> Thanks for your quick reply ! >> >> Luyao >> >>> John >>> >>> [...] >>> -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list