CPU_CLK_UNHALTED.THREAD Fixed PMU Event Reading Issue

[Osmanyasal]

Dear Perfmon Team,

We encountered an issue while attempting to read the CPU_CLK_UNHALTED.THREAD fixed PMU event, as it consistently returned 0 on four different systems. However, when configuring another fixed performance event (its reference cycles version), it worked as expected. What’s more surprising is that monitoring this event using its programmable counter event code worked correctly. We are curious if there might be an underlying issue we are unaware of.

Details are provided below.
Thank you for your assistance.

Best regards

================= PERFMON EVENT ===============

We are interested in CPU_CLK_UNHALTED.THREAD (doesn't count) and CPU_CLK_UNHALTED.REF_TSC (counts well)
We put the "perf" tool output but our tool (which uses perf_event_open kernel call) also result in 0.

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This is my laptop which support icl events.

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This is one of our machines
https://www.intel.com/content/www/us/en/products/sku/120485/intel-xeon-gold-6140-processor-24-75m-cache-2-30-ghz/specifications.html

==================
And this is another machine
[Products formerly Skylake](https://www.intel.com/content/www/us/en/products/sku/126697/intel-core-i97960x-xseries-processor-22m-cache-up-to-4-20-ghz/specifications.html)

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And This is the other machine
https://www.intel.com/content/www/us/en/products/sku/232167/intel-core-i913900ks-processor-36m-cache-up-to-6-00-ghz/specifications.html

=============== THE SUPRISING PART ================

For this event, this is the corresponding programmable event code for all given machines UNHALTED_CORE_CYCLES = 0x3c, which seems working.

My Laptop:

Xeon machine:

i9 machine:

the other i9 machine