Hello Kazimierz, The rdpmc instruction can't be used to read the fixed counter on some VIA Nano CPU's. We're trying to figure out which ones work and which ones don't work.
Can you provide CPU information from /proc/cpuinfo for your VIA Nano U3500 and VIA Eden X2 U4200 CPU's? Can you also provide the kernel boot messages for your working VIA Eden X2 U4200? The most interesting part is about the performance events. Example from my VIA Nano L2200: [ 1.009527] smpboot: CPU0: Centaur VIA Nano processor L2200@1600MHz (family: 0x6, model: 0xf, stepping: 0x2) [ 1.011855] Performance Events: [ 1.011858] core: Welcome to zhaoxin pmu! [ 1.019298] core: Version check pass! [ 1.023297] ZXC events, zhaoxin PMU driver. [ 1.027299] ... version: 2 [ 1.031297] ... bit width: 40 [ 1.035297] ... generic registers: 3 [ 1.039297] ... value mask: 000000ffffffffff [ 1.043297] ... max period: 0000007fffffffff [ 1.047297] ... fixed-purpose events: 3 [ 1.051297] ... event mask: 0000000700000007
