Re: [PATCH v6 1/2] qom: new object to associate device to numa node

[Ankit Agrawal]

Thanks Jonathan for the review.

> As per reply to the cover letter I definitely want to see SRAT table dumps
> in here though so we can easily see what this is actually building.

Ack.

> I worry that some OS might make the assumption that it's one GI node
> per PCI device though. The language in the ACPI specification is:
> 
> "The Generic Initiator Affinity Structure provides the association between _a_
> generic initiator and _the_ proximity domain to which the initiator belongs".
> 
> The use of _a_ and _the_ in there makes it pretty explicitly a N:1 
> relationship
> (multiple devices can be in same proximity domain, but a device may only be 
> in one).
> To avoid that confusion you will need an ACPI spec change.  I'd be happy to
> support

Yeah, that's a good point. It won't hurt to make the spec change to make the
possibility of the association between a device with multiple domains.

> The reason you can get away with this in Linux today is that I only 
> implemented
> a very minimal support for GIs with the mappings being provided the other way
> around (_PXM in a PCIe node in DSDT).  If we finish that support off I'd 
> assume

Not sure if I understand this. Can you provide a reference to this DSDT related
change?

> Also, this effectively creates a bunch of separate generic initiator nodes
> and lumping that under one object seems to imply they are in general connected
> to each other.
> 
> I'd be happier with a separate instance per GI node
> 
>  -object acpi-generic-initiator,id=gi1,pci-dev=dev1,nodeid=10
>  -object acpi-generic-initiator,id=gi2,pci-dev=dev1,nodeid=11
> etc with the proviso that anyone using this on a system that assumes a one
> to one mapping for PCI
>
> However, I'll leave it up to those more familiar with the QEMU numa
> control interface design to comment on whether this approach is preferable
> to making the gi part of the numa node entry or doing it like hmat.

> -numa srat-gi,node-id=10,gi-pci-dev=dev1

The current way of acpi-generic-initiator object usage came out of the 
discussion
on v1 to essentially link all the device NUMA nodes to the device.
(https://lore.kernel.org/all/20230926131427.1e441670.alex.williamson@redhat.com/)

Can Alex or David comment on which is preferable (the current mechanism vs 1:1
mapping per object as suggested by Jonathan)?