From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: WARNING: at /usr/src/modules/kvm/mmu.c:390 account_shadowed() Date: Sat, 26 Apr 2008 11:08:46 +0300 Message-ID: <4812E30E.2030808@qumranet.com> References: <480ED76E.9040400@qumranet.com> <20080424171421.GA14073@dmt> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, Thomas Cataldo To: Marcelo Tosatti Return-path: In-Reply-To: <20080424171421.GA14073@dmt> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Marcelo Tosatti wrote: > On Wed, Apr 23, 2008 at 09:30:06AM +0300, Avi Kivity wrote: > >>> as I got no reply, I guess it is a bad setup on my part. If that might >>> help, this happenned while I was doing a "make -j" on webkit svn tree >>> (ie. heavy c++ compilation workload) . >>> >>> >>> >> No this is not bad setup. No amount of bad setup should give this warning. >> >> You didn't get a reply because no one knows what to make of it, and >> because it's much more fun to debate endianess or contemplete guests >> with eighty thousand disks than to fix those impossible bugs. If you >> can give clear instructions on how to reproduce this, we will try it >> out. Please be sure to state OS name and versions for the guest as well >> as the host. >> > > It is valid to have more than PAGES_PER_HPAGE in the largepage's > shadowed count. If the gpte read races with a pte-update-from-guest (and > the pte update results in a different sp->role), it might account twice > for a single gfn. > > Such "zombie" shadow pages should eventually be removed through > recycling, allowing for instantiation of a large page, unless references > can be leaked. Can't spot such leakage problem though. > > That strikes me as unlikely (though a valid scenario). An alternative explanation is that we're seeing a nonpae guest, so each page can be shadowed in two different roles (two quadrants for a pte page) or even four (for a pgd page). Thomas, are you running a 32-bit nonpae guest? -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone