Hi, Jonathan, Jonathan Cameron <jonathan.came...@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....@redhat.com/ > https://lore.kernel.org/qemu-devel/74e2845c5f95b0c139c79233ddb65bb17f2dd679.1710282274.git....@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
