From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Longpeng (Mike)" Subject: [Question] About the behavior of HLT in VMX guest mode Date: Mon, 13 Mar 2017 15:12:50 +0800 Message-ID: <58C64672.1070706@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit To: kvm Return-path: Received: from szxga03-in.huawei.com ([45.249.212.189]:4404 "EHLO dggrg03-dlp.huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750846AbdCMHOI (ORCPT ); Mon, 13 Mar 2017 03:14:08 -0400 Sender: kvm-owner@vger.kernel.org List-ID: Hi guys, I'm confusing about the behavior of HLT instruction in VMX guest mode. I set "hlt exiting" bit to 0 in VMCS, and the vcpu didn't vmexit when execute HLT as expected. However, I used powertop/cpupower on host to watch the pcpu's c-states, it seems that the pcpu didn't enter C1/C1E state during this period. I searched the Intel spec vol-3, and only found that guest MWAIT won't entering a low-power sleep state under certain conditions(ch 25.3), but not mentioned HLT. My questions are 1) Does executing HLT instruction in guest-mode won't enter C1/C1E state ? 2) If it won't, then whether it would release the hardware resources shared with another hyper-thread ? Any suggestion would be greatly appreciated, thanks! -- Regards, Longpeng(Mike)