Re: [PATCH 0/6 qemu] acpi: NUMA nodes for CXL HB as GP + complex NUMA test.

[Huang, Ying]

Hi, Jonathan,

Jonathan Cameron <Jonathan.Cameron@huawei.com> writes:

> ACPI 6.5 introduced Generic Port Affinity Structures to close a system
> description gap that was a problem for CXL memory systems.
> It defines an new SRAT Affinity structure (and hence allows creation of an
> ACPI Proximity Node which can only be defined via an SRAT structure)
> for the boundary between a discoverable fabric and a non discoverable
> system interconnects etc.
>
> The HMAT data on latency and bandwidth is combined with discoverable
> information from the CXL bus (link speeds, lane counts) and CXL devices
> (switch port to port characteristics and USP to memory, via CDAT tables
> read from the device).  QEMU has supported the rest of the elements
> of this chain for a while but now the kernel has caught up and we need
> the missing element of Generic Ports (this code has been used extensively
> in testing and debugging that kernel support, some resulting fixes
> currently under review).
>
> Generic Port Affinity Structures are very similar to the recently
> added Generic Initiator Affinity Structures (GI) so this series
> factors out and reuses much of that infrastructure for reuse
> There are subtle differences (beyond the obvious structure ID change).
>
> - The ACPI spec example (and linux kernel support) has a Generic
>   Port not as associated with the CXL root port, but rather with
>   the CXL Host bridge. As a result, an ACPI handle is used (rather
>   than the PCI SBDF option for GIs). In QEMU the easiest way
>   to get to this is to target the root bridge PCI Bus, and
>   conveniently the root bridge bus number is used for the UID allowing
>   us to construct an appropriate entry.
>
> A key addition of this series is a complex NUMA topology example that
> stretches the QEMU emulation code for GI, GP and nodes with just
> CPUS, just memory, just hot pluggable memory, mixture of memory and CPUs.
>
> A similar test showed up a few NUMA related bugs with fixes applied for
> 9.0 (note that one of these needs linux booted to identify that it
> rejects the HMAT table and this test is a regression test for the
> table generation only).
>
> https://lore.kernel.org/qemu-devel/2eb6672cfdaea7dacd8e9bb0523887f13b9f85ce.1710282274.git.mst@redhat.com/
> https://lore.kernel.org/qemu-devel/74e2845c5f95b0c139c79233ddb65bb17f2dd679.1710282274.git.mst@redhat.com/
>

Thanks a lot for your work!

I need this to test some memory tiering kernel patches.  I found the
following git branch,

https://gitlab.com/jic23/qemu/-/commits/cxl-2024-03-05/?ref_type=heads

Can I use that branch directly?

And, can you share an example qemu command line to setup Genport, CDAT,
and HMAT?

--
Best Regards,
Huang, Ying