PMON Events for VT-d Scalable Mode IOMMU on Emerald Rapids

[Leshna]

I am trying to measure the performance of the IOMMU translation cache on a Emerald Rapids  using pcm-iio. My system is running with VT-d enabled in Scalable Mode.

For event sel 0x41, I can only see IOMMU memory accesses (umask=0xc0)
But all other events with event selector 0x41 give 0 values i.e.:

• ev_sel=0x41, umask=0x01 (Cache Lookup)
• All page-size hit counters (e.g., ev_sel=0x41 with umask=0x02 for 2M hits, umask=0x04 for 1G hits, etc.)

These non-working events consistently read zero, even under a heavy DMA workload that generates traffic for the working counters.

Any guidance or pointers for these specific Scalable Mode counters would be greatly appreciated.

Thank you.