Le 11/02/2023 à 02:53, Dan Williams a écrit :
Brice Goglin wrote: [..]By the way, once configured in system ram, my CXL ram is merged into an existing "normal" NUMA node. How do I tell Qemu that a CXL region should be part of a new NUMA node? I assume that's what's going to happen on real hardware?We don't yet have kernel code to deal with assigning a new NUMA node. Was on the todo list in last sync call I think.In fact, there is no plan to support "new" NUMA node creation. A node can only be onlined / populated from set of static nodes defined by platform-firmware. The set of static nodes is defined by the union of all the proximity domain numbers in the SRAT as well as a node per CFMWS / QTG id. See: fd49f99c1809 ACPI: NUMA: Add a node and memblk for each CFMWS not in SRAT ...for the CXL node enumeration scheme. Once you have a node per CFMWS then it is up to CDAT and the QTG DSM to group devices by window. This scheme attempts to be as simple as possible, but no simpler. If more granularity is necessary in practice, that would be a good discussion to have soonish.. LSF/MM comes to mind.
Actually I was mistaken, there's already a new NUMA node when creating a region under Qemu, but my tools ignored it because it's empty. After daxctl online-memory, things look good. Can you clarify your above sentences on a real node? If I connect two memory expanders on two slots of the same CPU, do I get a single CFMWS or two? What if I connect two devices to a single slot across a CXL switch? Brice
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