Re: [PATCH for-6.0 0/6] Add HMP/QMP commands to query accelerator

[Claudio Fontana]

On 11/19/20 4:46 PM, Roman Bolshakov wrote:
> On Thu, Nov 19, 2020 at 03:41:53PM +0100, Claudio Fontana wrote:
>> On 11/16/20 2:10 PM, Roman Bolshakov wrote:
>>> Management applications have no way to determine if certain accelerator
>>> is available. That complicates discovery of non-KVM accelerators.
>>
>> are we thinking about how to make this future-proof when it comes to
>> modularization efforts, ie, when we get to fully modularized
>> accelerator plugins?
>>
>> Maybe too soon to consider, but still worth mentioning on my side I think.
>>
> 
> Hi Claudio,
> 
> I'd be happy to do it future-proof if you have something on the mind.
> As far as I understand from the discussion, if we have /machine/accel
> container, we can use QOM to query properties of the container including
> accel name:
> qom-get /machine/accel/type
> 
> Thanks,
> Roman
> 

My understanding is very limited here, especially when it comes then to how 
libvirt f.e. uses this,

I wonder how to make sure that libvirt does not query the currently selected 
accelerator "too early",
ie before it has been finally selected (what in the other series I called the 
INIT_ACCEL_CPU time),

and how to query "available/supported" accelerators in a way that accounts for 
the fact that the plugin might not be loaded or available.

I guess this is a larger question about how libvirt detects modularized 
features in QEMU, when those features are (or are not) present only in an 
external binary plugin.

Ciao,

Claudio