Couldn't use x86 emulators, AVD manager shows warning "/dev/kvm is not found" and telling me to edit BIOS security setting to enable VT-x.
Re-installing HAXM resolved my problem Steps:
SDK Manager -> Extras -> Intel x86 Emulator Accelerator (HAXM installer)
is installed<sdk>
/extras/intel/Hardware_Accelerated_Execution_Manager/
./HAXM\ installation -u
./HAXM\ installation