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

[John Ferlan]

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.

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.

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.

John

> 
> Thanks for your quick reply !
> 
> Luyao
> 
>> John
>>
>> [...]
>>
>