SGI UV GRU (Global Reference Unit) coprocessor
A specialized coprocessor built into the UV Hub ASIC of SGI's UV-series scale-up servers (UV 100, 1000, 2000, and later UV 300 / MC990 X), used in large NUMA machines from roughly the early 2010s through the mid-2010s to accelerate cross-node memory references and message passing over the NUMAlink interconnect.
recommendation
Worth keeping but flagging as legacy because the hardware is tied to SGI UV systems that HPE's newer NUMAlink 8 Superdome Flex platforms superseded around 2017, and nothing comparable has shipped since. HPE was still issuing security bulletins for SGI UV 300 and MC990 X into 2022 and 2023, so an installed base remains, and the code continues to absorb routine memory-management API updates upstream with no removal effort in sight. A short note documenting that this serves only legacy SGI UV deployments would help future cleanup decisions.
repository signals
sources
- lore.kernel.org
The driver still receives upstream maintenance touches in current kernels; grumain.c was updated by an MM API rename series in February 2026.
- support.hpe.com
HPE was still issuing security bulletins covering SGI UV300 in 2023, indicating an installed base and vendor support tail rather than a current-volume product.
- support.hpe.com
HPE listed SGI UV 300 and Integrity MC990 X in a 2022 security bulletin, further showing the platform remained supported as legacy enterprise hardware.
- en.wikipedia.org
NUMAlink 7 systems included SGI UV 300 / UV 300H / MC990 X, while newer HPE scale-up systems moved to NUMAlink 8 (Superdome Flex), implying the GRU-equipped UV line had been superseded by 2017.
- techpubs.jurassic.nl
The GRU is a specialized coprocessor inside the SGI UV Hub ASIC and the manual applies to SGI UV 100/1000/2000 systems, confirming this is niche platform-specific hardware rather than generic x86 functionality.
codex reasoning notes (technical)
Lore evidence came from `mcp__lore_http__.lore_file_timeline` and `lore_activity` on `drivers/misc/sgi-gru/grumain.c`; that shows ongoing treewide/MM compatibility maintenance through 2026 and no observed removal signal in the successful lore queries. HPE bulletin URLs were obtained by `web.search_query` and indicate a lingering supported install base in 2022-2023, but not evidence of new 2025 sales. The NUMAlink and SGI UV GRU documentation URLs were also obtained by `web.search_query`; together they show GRU is tied to older SGI UV generations that were superseded by newer HPE NUMAlink 8 systems. Recommendation is `keep-annotate`: hardware appears obsolete and low-deployment, but upstream still pays maintenance cost and there is no clear replacement driver or active removal thread in the gathered evidence.