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

[Jason Gunthorpe]

On Tue, Jan 09, 2024 at 06:02:03PM +0100, David Hildenbrand wrote:
> > Given that, an alternative proposal that I think would work
> > for you would be to add a 'placeholder' memory node definition
> > in SRAT (so allow 0 size explicitly - might need a new SRAT
> > entry to avoid backwards compat issues).
> 
> Putting all the PCI/GI/... complexity aside, I'll just raise again that for
> virtio-mem something simple like that might be helpful as well, IIUC.
> 
>       -numa node,nodeid=2 \
>       ...
>       -device virtio-mem-pci,node=2,... \
> 
> All we need is the OS to prepare for an empty node that will get populated
> with memory later.

That is all this is doing too, the NUMA relationship of the actual
memory is desribed already by the PCI device since it is a BAR on the
device.

The only purpose is to get the empty nodes into Linux :(

> So if that's what a "placeholder" node definition in srat could achieve as
> well, even without all of the other acpi-generic-initiator stuff, that would
> be great.

Seems like there are two use quite similar cases.. virtio-mem is going
to be calling the same family of kernel API I suspect :)

Jason