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On Lenovo Laptop with Ryzen APU I get the message during boot:

pci 0000:00:00.2: AMD-Vi: Unable to read/write to IOMMU perf counter.

(dmsg | grep IOMMU)


Reproducible: Always

Steps to Reproduce:
Hardware for reproducing is needed.
Actual Results:  
pci 0000:00:00.2: AMD-Vi: Unable to read/write to IOMMU perf counter.

Expected Results:  
pci 0000:00:00.2: AMD-Vi: IOMMU performance counters supported
pci 0000:00:00.2: AMD-Vi: Found IOMMU cap 0x40
perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank).

The expected result I got when booting Ubuntu 20.04. Seems to be that a certain
parameter in kernel config needs to be set.