Separating between the ordinary Hall effect and anomalous Hall effect in the paramagnetic phase of Mn1-xFexSi reveals an ordinary Hall effect sign inversion associated with the hidden quantum critical (QC) point x* similar to 0.11. The effective hole doping at intermediate Fe content leads to verifiable predictions in the field of fermiology, magnetic interactions, and QC phenomena in Mn1-xFexSi. The change of electron and hole concentrations is considered as a "driving force" for tuning the QC regime in Mn1-xFexSi via modifying the Ruderman-Kittel-Kasuya-Yosida exchange interaction within the Heisenberg model of magnetism.