AMD IOMMU perf counters on Zen2
amonakov at ispras.ru
Tue May 26 23:03:05 UTC 2020
I'd like to use IOMMU perf counters on a Zen 2 CPU (Ryzen 4500U, Renoir SoC).
Unfortunately, init_iommu_perf_ctr fails because val2 != val, i.e. the
counter appears not writable. However, if I patch the kernel to skip this
check, the counters seem to increment when configured with perf tool.
Do you know why the counter might appear not writable in newer CPUs?
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