Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758617AbYGPWtA (ORCPT ); Wed, 16 Jul 2008 18:49:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753599AbYGPWsv (ORCPT ); Wed, 16 Jul 2008 18:48:51 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:56329 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbYGPWsu (ORCPT ); Wed, 16 Jul 2008 18:48:50 -0400 Subject: KVM overflows the stack From: Dave Hansen To: Avi Kivity Cc: "linux-kernel@vger.kernel.org" , kvm-devel , "Anthony N. Liguori [imap]" In-Reply-To: <1216244660.8711.6.camel@nimitz> References: <1206479576.7562.21.camel@nimitz.home.sr71.net> <47EA1C63.8010202@qumranet.com> <1206550329.7883.5.camel@nimitz.home.sr71.net> <47EA80AC.4070204@qumranet.com> <1206551794.7883.7.camel@nimitz.home.sr71.net> <47EB6AAC.3040607@qumranet.com> <47EB7281.6070300@qumranet.com> <1206629709.7883.30.camel@nimitz.home.sr71.net> <47EBB63E.2060306@qumranet.com> <1212445810.8211.9.camel@nimitz.home.sr71.net> <48469BDA.3050206@qumranet.com> <1212738105.7837.3.camel@nimitz> <48512028.3070104@qumranet.com> <1216148242.25942.6.camel@nimitz> <1216244660.8711.6.camel@nimitz> Content-Type: text/plain Date: Wed, 16 Jul 2008 15:48:47 -0700 Message-Id: <1216248527.11664.9.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2139 Lines: 60 On Wed, 2008-07-16 at 14:44 -0700, Dave Hansen wrote: > On a suggestion of Anthony's, I tried a defconfig kernel. > > It is now bombing out on an assertion in the lapic code: > > http://sr71.net/~dave/linux/2.6.26-oops1.txt I think I found it!!! $ (objdump -d kvm.ko ; objdump -d kvm-intel.ko ) | egrep 'sub.*0x...,.*esp|>:' | egrep sub -B1 00001a90 : 1a9a: 81 ec 60 06 00 00 sub $0x660,%esp -- 00004e90 : 4e9d: 81 ec 6c 08 00 00 sub $0x86c,%esp -- 00005900 : 5903: 81 ec 34 05 00 00 sub $0x534,%esp -- 0000d4f0 : d4f8: 81 ec 1c 01 00 00 sub $0x11c,%esp -- 0000dfd0 : dfd8: 81 ec 1c 01 00 00 sub $0x11c,%esp -- 0000f390 : f3a1: 81 ec 28 02 00 00 sub $0x228,%esp We're simply overflowing the stack. I changed all of the large on-stack allocations to 'static', and it actually boots now. I know 'static' isn't safe, but it was good for a quick test. A 'make stackcheck' confirms this: dave@nimitz:~/kernels/linux-2.6.git$ make checkstack objdump -d vmlinux $(find . -name '*.ko') | \ perl /home/dave/kernels/linux-2.6.git-t61/scripts/checkstack.pl i386 0x000042d3 kvm_arch_vcpu_ioctl [kvm]: 2148 0x000012e3 kvm_vcpu_ioctl [kvm]: 1620 0x00004a83 kvm_arch_vm_ioctl [kvm]: 1332 0x00009a26 airo_get_aplist [airo]: 1140 0x00009b76 airo_get_aplist [airo]: 1140 0x00009c82 airo_get_aplist [airo]: 1140 ... In other words, kvm has the top 3 stack users in my kernel. As you can see from my trace above, these things also get called with super-long stacks already. Man. That sucked to find. Avi, how would you like this fixed? I'd be happy to prepare some patches. Do you have a particular approach that you think we should use? Just make the big objects dynamically allocated? -- Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/