Speaker
Description
Modern GPUs and dedicated AI accelerators are increasingly connected through scale-up interconnect fabrics such as AMD xGMI today and UALink in the near future. Yet Linux lacks common topology infrastructure for reporting, vendor-neutrally, which accelerators are directly connected, through which ports, and in what state. Vendors expose fragments privately — e.g. amdgpu's xGMI sysfs — and prior per-driver proposals, such as XeLink, never became shared Linux infrastructure. As a result, topology semantics are being defined by vendor-private uAPIs rather than by a shared Linux control-plane contract for monitoring and fabric management.
Building on the LPC 2025 "Toward Mainline Linux Support for UALink" BoF, we propose DRM Fabric: a vendor-neutral, protocol-agnostic DRM topology infrastructure for scale-up interconnects, using the model:
fabric → endpoint → port → peer
Vendor drivers populate it through a thin provider API; userspace queries it through drm-fabric, a YAML-defined generic-netlink family consumed through ynl tooling, following the netlink uAPI pattern drm_ras introduced to DRM. No data path: load/store traffic and memory semantics remain in the vendor driver, so the infrastructure remains valid across vendors and fabrics.
The implementation is split into two RFC series. Phase 1 targets provider-owned fabrics, such as an xGMI-like implementation, where the driver discovers topology and reports it read-only to userspace, including notifications, optional port statistics, and consistent multipart enumeration. Phase 2 adds privileged provisioning for software-defined, UALink-style fabrics: creating fabric containers, attaching orphan endpoints, setting administrative state, and provisioning peers on userspace-managed ports, while providers continue to report actual hardware state. The RFCs include the core infrastructure, an in-tree synthetic provider (fabricsim, modeled on netdevsim), and KUnit plus pyynl/kselftests exercising the infrastructure and uAPI end-to-end without hardware. The next step is a hardware-backed provider for an already-shipping scale-up fabric.
We want LPC feedback on the DRM representation, the boundary between provider-owned topology and privileged userspace provisioning, whether the proposed provisioning primitives are sufficient, and how AMD, Intel, UALink Consortium members, and other accelerator vendors should co-develop the common infrastructure and provider interfaces.