microsoft / microsoft/openvmm

openhcl/aarch64: pmu reported via DT on kernel 6.12 seems to be missing something

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bug
Dominant language
Rust
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Description

I see the following with the 6.12 OpenHCL kernel:

[kmsg]: [0.031884] armv8-pmu pmu: hw perfevents: no irqs for PMU, sampling events not supported
[kmsg]: [0.032059] hw perfevents: enabled with armv8_pmuv3 PMU driver, 6 (0,8000001f) counters available

the sampling events not supported leads me to believe perf won't work, but it needs further investigation in the kernel what else needs to be specified in dt versus when we describe this in ACPI.

In the Linux direct 6.1, no such samping events not supported print exists, but it's unclear if perf actually works in 6.1 as I didn't try it.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by comparing the OpenHCL kernel 6.12 device-tree PMU description with how PMU details are described through ACPI. Reproduce the armv8-pmu messages and investigate whether perf sampling works; done means identifying any missing device-tree specification and confirming the corrected behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
linux
Domain
operating-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
32/100

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