Description of problem: When the processor is idle，low-power idle states (C-states) can be used to save power. For Zhaoxin processors，there are two methods to enter idle states. One is HLT instruction and legacy method of I/O reads from the ACPI-defined register (known as P_LVLx)，the other one is MWAIT instruction with idle states hints. Default for legacy operating system，HLT and P_LVLx I/O reads are used for Zhaoxin Processors to enter idle states, but we have checked on some Zhaoxin platform that MWAIT instruction is more efficient than P_LVLx I/O reads and HLT, so we add MWAIT Cx support for Zhaoxin Processors. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: Case1: 在BIOS里设置MWAIT support为Enable；Linux kernel使用MWAIT指令进入到Core Cx； 1）dmesg 查看kernel boot log里，应该能看到“Monitor-Mwait will be used to enter C1/C2/Cx state” 2）在Linux OS下dump Cstate信息如下 # cat /sys/devices/system/cpu/cpu0/cpuidle/state*/desc CPUIDLE CORE POLL IDLE ACPI FFH MWAIT 0x0 ACPI FFH MWAIT 0x10 ACPI FFH MWAIT 0x20 ACPI FFH MWAIT 0x30 3）确认CPU能够进入到package Cx；package C2/C3/C4 residency（即0x870-0x87B）有变化； hexdump -C -s 0x870 -n 16 /dev/port Case2：kernel boot时，在grub中设置idle=nomwait，能够切换到Legacy P_LVLx IOR Cx 方式 1） dmesg 查看kernel boot log里，不会再看到“Monitor-Mwait will be used to enter C1/C2/Cx state” 2） 在Linux OS下dump Cstate信息如下 # cat /sys/devices/system/cpu/cpu0/cpuidle/state*/desc CPUIDLE CORE POLL IDLE ACPI HLT ACPI IOPORT 0x814 ACPI IOPORT 0x815 ACPI IOPORT 0x816 3） 确认CPU能够进入到package Cx； package C2/C3/C4 residency（即0x870-0x87B）有变化； hexdump -C -s 0x870 -n 16 /dev/port Actual results: Expected results: 不管使用P_LVLx I/O reads 还是MWAIT instruction，core都能进入指定的idle states，整个CPU package能够进入相应的package c-states。 Additional info:
merged: https://gitee.com/anolis/cloud-kernel/pulls/842