From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 0/3] KVM: Tie MWAIT/HLT/PAUSE interception to initially disabled capabilities Date: Wed, 29 Nov 2017 02:20:34 +0200 Message-ID: <20171129021958-mutt-send-email-mst@kernel.org> References: <1511615373-32615-1-git-send-email-jschoenh@amazon.de> <8971d9e0-388c-9934-1ab2-33508cbbeb8f@redhat.com> <20171128160528-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan =?iso-8859-1?Q?H=2E_Sch=F6nherr?= , Radim =?utf-8?B?S3LEjW3DocWZ?= , Joerg Roedel , KarimAllah Ahmed , kvm@vger.kernel.org To: Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:37742 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751402AbdK2AUh (ORCPT ); Tue, 28 Nov 2017 19:20:37 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Nov 29, 2017 at 01:07:32AM +0100, Paolo Bonzini wrote: > On 28/11/2017 15:08, Michael S. Tsirkin wrote: > > I think guests still want some way to halt when > > giving up CPU for a long time. > > > > If you are not worried about guests entering low power states, > > then you only need MWAIT and maybe PAUSE. > > > > HLT within guest only makes sense if you do not want to > > allow guest to enter power state. > > > > If you don't exit on any of these, you want some other way > > to actually halt the VCPU. > > If you want to do something in userspace, send a signal. Otherwise, it > doesn't really matter (if you have a dedicated physical CPU) whether the > task is runnable or not, as long as the CPU isn't in C0. > > Paolo If VCPU wants to give up its timeslice, how is it supposed to do it if all exits are blocked? -- MST