From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: High vm-exit latencies during kvm boot-up/shutdown Date: Thu, 25 Oct 2007 20:02:42 +0200 Message-ID: <4720DA42.6090300@qumranet.com> References: <471D2D8C.1080202@web.de> <10EA09EFD8728347A513008B6B0DA77A02441127@pdsmsx411.ccr.corp.intel.com> <471D96DC.7070809@web.de> <10EA09EFD8728347A513008B6B0DA77A024414D9@pdsmsx411.ccr.corp.intel.com> <471DBA1A.2080108@web.de> <471DC311.2050003@qumranet.com> <471DF76B.7040001@siemens.com> <471E02F7.6080408@qumranet.com> <471E0818.6060405@siemens.com> <471E1290.2000208@qumranet.com> <471E1A77.90808@siemens.com> <471E1DCD.5040301@qumranet.com> <471E21D7.3000309@siemens.com> <471E238E.6040005@qumranet.com> <471E27B0.1090001@siemens.com> <471E29C5.1060807@qumranet.com> <471F0464.4000704@siemens.com> <471F07C0.8040104@qumranet.com> <471F0D57.3020209@siemens.com> <471F116D.9080903@qumranet.com> <471F7143.8040406@siemens.com> <471F7865.7070506@qumranet.com> <4720D76D.7070300@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Jan Kiszka Return-path: In-Reply-To: <4720D76D.7070300-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Jan Kiszka wrote: > Avi Kivity wrote: > >> Jan Kiszka wrote: >> >>> Got it! It's wbinvd from smm_init in rombios32.c! Anyone any comments on >>> this? >>> >>> >> Ha! A real life 300usec instruction! >> >> Unfortunately, it cannot be trapped on Intel (it can be trapped on >> AMD). Looks like a minor hole in VT, as a guest can generate very high >> latencies this way. >> > > I unfortunately do not have an AMD box at hand to test (I obviously > order the wrong processor then...), but does this mean it is trapped by > kvm-amd already? Or would there be more work required on that side? > > There's a two-liner required to make it work. I'll add it soon. >> For our bios, we can remove it, but there's no way to ensure an >> untrusted guest doesn't use it. >> > > Yep. Any ideas if and at which stages (bootup, normal operation) Windows > is issues wbinvd noise? > No idea. I'll check it with an AMD machine. I'd be surprised it it did that during normal operation. It's also conceivable that it doesn't issue it at all. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/