Re: [Qemu-devel] [PATCH v1 2/7] pcihp: overwrite hotplug handler recursively from the start

[David Hildenbrand <david@redhat.com>]

On 02.11.18 14:00, Igor Mammedov wrote:
> On Fri, 2 Nov 2018 12:43:10 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
>> On 01.11.18 15:10, Igor Mammedov wrote:
>>> On Wed, 24 Oct 2018 12:19:25 +0200
>>> David Hildenbrand <david@redhat.com> wrote:
>>>   
>>>> For now, the hotplug handler is not called for devices that are
>>>> being cold plugged. The hotplug handler is setup when the machine
>>>> initialization is fully done. Only bridges that were cold plugged are
>>>> considered.
>>>>
>>>> Set the hotplug handler for the root piix bus directly when realizing.
>>>> Overwrite the hotplug handler of bridges when hotplugging/coldplugging
>>>> them.
>>>>
>>>> This will now make sure that the ACPI PCI hotplug handler is also called
>>>> for cold-plugged devices (also on bridges) and for bridges that were
>>>> hotplugged.
>>>>
>>>> When trying to hotplug a device to a hotplugged bridge, we now correctly
>>>> get the error message
>>>>  "Unsupported bus. Bus doesn't have property 'acpi-pcihp-bsel' set"
>>>> Insted of going via the standard PCI hotplug handler.  
>>> Erroring out is probably not ok, since it can break existing setups
>>> where SHPC hotplugging to hotplugged bridge was working just fine before.  
>>
>> The question is if it actually was supposed (and eventually did) work.
> I think it works now, it's QEMU 'ACPI hotplug hack' (which exists for
> the sake of Windows) limitation. We weren't able to dynamically add
> ACPI description for hotplugged bridge, so it was using native hotplug.
> Now theoretically we can load tables dynamically but that, would add
> maintenance nightmare (versioned tables) and would be harder to debug.
> I'd rather not go that direction and keep current limited version,
> suggesting users to use native hotplug if guest is capable.

Alright I'll keep current behavior (checking if the bridge is hotplugged
or coldplugged). Thanks!


-- 

Thanks,

David / dhildenb