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Intel Posts New Linux Patches Looking To Re-Enable ENQCMD Ahead Of Sapphire Rapids
The ENQCMD instruction (and ENQCMDS) allows atomically submitting a work descriptor to a device and part of the Data Streaming Accelerator debuting as part of next year's Sapphire Rapids processors. But the initial Linux kernel support code was in poor shape -- including insufficient protection against FPU state modification -- and led to it being disabled upstream. Intel originally upstreamed the ENQCMD work since last year.
With this set of patches, ENQCMD is looking to be re-enabled. We'll see though if the upstream kernel maintainers are happy now with the state of the code or further alterations will be required. If all goes well, the re-enabling could come for Linux 5.16 later this year -- still ahead of Sapphire Rapid's ramp in Q2.
While much of the Xeon Sapphire Rapids enablement for Linux has been completed for a while now, two other important pieces still settling down ahead of the next-gen Xeon Scalable is the Advanced Matrix Extensions (AMX) kernel-side support and x86 User Interrupts.