Re: [PATCH v5 1/2] qom: new object to associate device to numa node

[Ankit Agrawal <ankita@nvidia.com>]

Thanks Markus for the review.

>> Introduce a new acpi-generic-initiator object to allow host admin provide the
>> device and the corresponding NUMA nodes. Qemu maintain this association and
>> use this object to build the requisite GI Affinity Structure.
>
> Pardon my ignorance...  What makes this object an "initiator", and why
> is it "generic"?

In ACPI 6.3 (https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf),
a new table in System Resource Affinity Table called Generic initiator Affinity table
was introduced to describe devices such as heterogeneous processors and
accelerators, GPUs, and I/O devices with  integrated compute or DMA engines
(termed as Generic Initiator) that are present on the system. It is used to associate
a proximity domain with those devices.

You may refer 5.2.16.6 in the aforementioned link. This patch implements that
structure (Table 5-78) for Qemu ACPI.

>> An admin can provide the range of nodes through a uint16 array host-nodes
>> and link it to a device by providing its id. Currently, only PCI device is
>> supported. The following sample creates 8 nodes and link them to the PCI
>> device dev0:
>>
>> -numa node,nodeid=2 \
>> -numa node,nodeid=3 \
>> -numa node,nodeid=4 \
>> -numa node,nodeid=5 \
>> -numa node,nodeid=6 \
>> -numa node,nodeid=7 \
>> -numa node,nodeid=8 \
>> -numa node,nodeid=9 \
>> -device vfio-pci-nohotplug,host=0009:01:00.0,bus=pcie.0,addr=04.0,rombar=0,id=dev0 \
>> -object acpi-generic-initiator,id=gi0,pci-dev=dev0,host-nodes=2-9 \
>
> Does this link *all* NUMA nodes to dev0?
>
> Would an example involving two devices be more instructive?

Sure, updated in v6.

>> diff --git a/qapi/qom.json b/qapi/qom.json
>> index c53ef978ff..efcc4b8dfd 100644
>> --- a/qapi/qom.json
>> +++ b/qapi/qom.json
>> @@ -794,6 +794,21 @@
>>  { 'struct': 'VfioUserServerProperties',
>>    'data': { 'socket': 'SocketAddress', 'device': 'str' } }
>>
>> +##
>> +# @AcpiGenericInitiatorProperties:
>> +#
>> +# Properties for acpi-generic-initiator objects.
>> +#
>> +# @pci-dev: PCI device ID to be associated with the node
>> +#
>> +# @host-nodes: numa node list
>
> This feels a bit terse.  The commit message makes me guess this
> specifies the NUMA nodes to be linked to @pci-dev.  Correct?

Right, it could be made cleared. Done in v6.