From mboxrd@z Thu Jan 1 00:00:00 1970 From: Carsten Otte Subject: Re: soft lockup after stop/cont Date: Thu, 11 Oct 2007 12:57:38 +0200 Message-ID: <470E01A2.104@de.ibm.com> References: <20071010080152.GA27601@jim.sh> <470C87AB.6050900@qumranet.com><20071010185443.GA14525@jim.sh> <470DE6F8.9090801@de.ibm.com> <10EA09EFD8728347A513008B6B0DA77A02364AD6@pdsmsx411.ccr.corp.intel.com> Reply-To: carsteno-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: carsteno-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org, kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Jan Glauber1 , Avi Kivity To: "Dong, Eddie" Return-path: In-Reply-To: <10EA09EFD8728347A513008B6B0DA77A02364AD6-wq7ZOvIWXbNpB2pF5aRoyrfspsVTdybXVpNB7YpNyf8@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 Dong, Eddie wrote: > kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org wrote: >> Jim Paris wrote: >>> If I stop KVM in the monitor with "stop", wait a minute, and do >>> "cont", a Linux guest gives me a "BUG: soft lockup detected on >>> CPU#0". Is that expected behavior? >> We have the same behavior on s390 when running in a virtual >> environment. The issue is, that the guest physical cpu may be >> scheduled away while a timer runs down. I don't think there's anything >> kvm could do better regerding the soft lockup code. Soft lockup is >> just broken for virtualized environments and needs to be fixed. For >> the time being, just disable it in kconfig. >> > This is a well known issue, but we can fix by syncing TSC with PIT etc. > But doing this we need to froze guest TSC when a VP is descheduled. > > We enable this in Xen but feel it is too complicated so never wanna > to do same thing in KVM per previous discussion. There are some > side effect of course due to this. > > In Xen some time you will see PV domain soft lockup, but never in > hardware HVM :-) Hopefully Linux will have pv timer soon. Yes, virtual timers will be the right fix for it. I believe Jan has a patch for that. Am I mistaken Jan? [adding Jan to CC:] ------------------------------------------------------------------------- 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/