On 09.01.24 17:52, Jonathan Cameron wrote:
On Thu, 4 Jan 2024 10:39:41 -0700
Alex Williamson <alex.william...@redhat.com> wrote:
On Thu, 4 Jan 2024 16:40:39 +0000
Ankit Agrawal <ank...@nvidia.com> wrote:
Had a discussion with RH folks, summary follows:
1. To align with the current spec description pointed by Jonathan, we first do
a separate object instance per GI node as suggested by Jonathan. i.e.
a acpi-generic-initiator would only link one node to the device. To
associate a set of nodes, those number of object instances should be
created.
2. In parallel, we work to get the spec updated. After the update, we switch
to the current implementation to link a PCI device with a set of NUMA
nodes.
Alex/Jonathan, does this sound fine?
Yes, as I understand Jonathan's comments, the acpi-generic-initiator
object should currently define a single device:node relationship to
match the ACPI definition.
Doesn't matter for this, but it's a many_device:single_node
relationship as currently defined. We should be able to support that
in any new interfaces for QEMU.
Separately a clarification of the spec
could be pursued that could allow us to reinstate a node list option
for the acpi-generic-initiator object. In the interim, a user can
define multiple 1:1 objects to create the 1:N relationship that's
ultimately required here. Thanks,
Yes, a spec clarification would work, probably needs some text
to say a GI might not be an initiator as well - my worry is
theoretical backwards compatibility with a (probably
nonexistent) OS that assumes the N:1 mapping. So you may be in
new SRAT entry territory.
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.
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.
--
Cheers,
David / dhildenb
