From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: BUG_ON in mmu.c:436 Date: Sun, 30 Sep 2007 09:32:34 +0200 Message-ID: <46FF5112.3080206@qumranet.com> References: <20070923215548.GP7519@us.ibm.com> <46F76D46.7040502@qumranet.com> <20070924212649.GS7519@us.ibm.com> <46F82E36.7000402@codemonkey.ws> <20070928181915.GH7519@us.ibm.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: Ryan Harper Return-path: In-Reply-To: <20070928181915.GH7519-r/Jw6+rmf7HQT0dZR+AlfA@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 Ryan Harper wrote: > * Anthony Liguori [2007-09-24 16:39]: > >> Ryan Harper wrote: >> >>> * Avi Kivity [2007-09-24 02:57]: >>> >>> >>>> Ryan Harper wrote: >>>> >>>> >>>>> I've run into a nasty bug while trying to install a Linux guest using >>>>> VMware Server inside a kvm guest (full dmesg attached and recreate >>>>> instructions below bug). >>>>> >>>>> >>>>> >>>>> >>>> Can you reproduce this with AUDIT turned on (top of mmu.c)? AUDIT is >>>> very slow, so it's recommended to reduce guest memory as much as possible. >>>> >>>> >>> Working on it -- running for the better part of today with 256MB and I'm >>> still booting up the guest. I'll let you know how things go tomorrow. >>> Any thoughts on how to speed audit runs up other than lower guest >>> memory? >>> >>> >> savevm right before you're about to launch your test w/o audit enabled. >> then launch with loadvm and audit enabled and hit to launch your >> test. >> > > That was highly effective in getting as close to the fault as possible. > We may want to add a module parameter so that audit can be enabled and disabled at runtime when compiled in. > I ended up removing all callers to kvm_mmu_audit() and added one to > mmu.c:rmap_write_protect() write before the BUG_ON() fires. Here is the > kvm_mmu_audit() output the crash generates: > > > audit_write_protection: (rmap_write_protect()) shadow page has writable mappings: gfn 5297 role 112 > audit_write_protection: (rmap_write_protect()) shadow page has writable mappings: gfn 6d52 role 112 > audit_write_protection: (rmap_write_protect()) shadow page has writable mappings: gfn 659b role 12 > We need to bracket the error so that we know exactly where the problem starts to appear, and then enable debug (conditionally on rip and/or cr2) so that we have a full trace of what happens. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/