From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Host latency peaks due to kvm-intel Date: Sun, 26 Jul 2009 17:45:40 +0300 Message-ID: <4A6C6C14.4030805@redhat.com> References: <4A68A6E5.6010808@siemens.com> <4A68BD5D.1070302@gmail.com> <4A6981B0.3000008@siemens.com> <4A6B1C15.6090608@redhat.com> <4A6C6970.6060200@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Gregory Haskins , kvm-devel , RT , "Yang, Sheng" To: Jan Kiszka Return-path: In-Reply-To: <4A6C6970.6060200@web.de> Sender: linux-rt-users-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 07/26/2009 05:34 PM, Jan Kiszka wrote: > Avi Kivity wrote: > >> On 07/24/2009 12:41 PM, Jan Kiszka wrote: >> >>> Jan (who is now patching his guest to avoid wbinvd where possible) >>> >>> >>> >> Is there ever a case where it is required? What about under a >> hypervisor (i.e. check the hypervisor enabled bit). >> >> > > Reminds me of the discussion in '07 when I first stumbled over this :) : > Yes, the bochs bios could safely skip the wbinvd in qemu mode. But that > won't safe us from Linux and - far more problematic - Windows or any > binary-only guest which think they have to issue it. > > One may the close eyes, fire up the guest and then start the > time-critical host application in the hope that the guest remains calm > as long as it's up and running. But, well... > Given that it's now '09, how critical is the problem? Don't most cpus have vwbinvd now? If so, the real-time management application can simply refuse to run on such an old processor. -- error compiling committee.c: too many arguments to function