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And maybe to enforce it > > even stronger, your driver should fail to build if PREFERRED_CPU is > > disabled. Imagine a scenario when someone makes PREFERRED_CPU > > depending on some other config, but doesn't modify your driver. That > > way you'll build the STEAL_MONITOR successfully, but because > > PREFERRED_CPU is off, you'll end up with non-working functionality at > > best, or corrupted cpu_active_mask at worst. > > > > Sorry, i may not understand all the intricacies of kconfigs. > But, Since driver selects PREFERRED_CPU, and PREFERRED_CPU can't be enabled > individually, driver again can't depend on PREFERRED_CPU right? > > As per previous discussion, it is probably better that driver selects PREFERRED_CPU. > Keeping them both independent and selectable brings too many variations. > No? > > I guess you meant below. > > In kernel/Kconfig.preempt: > config PREFERRED_CPU > bool > depends on SMP && PARAVIRT > > Driver's Kconfig (this is there already) > config VIRT_STEAL_GOVERNOR > tristate "Virtual Steal Time Governor" > depends on SMP && PARAVIRT > select PREFERRED_CPU It's just another precaution. In a hypothetical case of making preferred CPUs config extended in future, one could keep the steal governor configuration consistent to avoid this situation: config PREFERRED_CPU depends on SMP && PARAVIRT && NEW_DEPENDENCY bool config VIRT_STEAL_GOVERNOR tristate "Virtual Steal Time Governor" depends on SMP && PARAVIRT # NEW_DEPENDENCY dependency missed select PREFERRED_CPU # Selection doesn't happen In sm_core.c: #if !IS_ENABLED(CONFIG_PREFERED_CPU) # error "Preferred CPUs is the requirement" #endif As said, it's only precaution for hypothetical case, but it makes you nice for those working on preferred CPUs in future. Thanks, Yury