From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Amon Subject: Re: Unable to single-step in kvm, always results in a resume Date: Thu, 28 Jan 2010 22:57:05 -0500 Message-ID: <4B625C91.3090406@xceedium.com> References: <4B55C05D.6030408@xceedium.com> <4B55CBA8.6040306@siemens.com> <4B55CBFF.5030900@siemens.com> <4B566CB5.7080804@xceedium.com> <4B56D62D.3060106@siemens.com> <4B5922BE.7030002@xceedium.com> <4B59BEF0.80407@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm To: Jan Kiszka Return-path: Received: from 66-243-76-94.focaldata.net ([66.243.76.94]:4950 "EHLO mail.xceedium.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1756600Ab0A2Dvd (ORCPT ); Thu, 28 Jan 2010 22:51:33 -0500 Received: from amon.xceedium.com by mail.xceedium.com (MDaemon PRO v9.6.3) with ESMTP id md50000624314.msg for ; Thu, 28 Jan 2010 22:52:21 -0500 In-Reply-To: <4B59BEF0.80407@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: Jan Kiszka wrote: > Nicholas Amon wrote: > >> So now I can step instruction but my breakpoints do not work. I have >> verified that disabling kvm restores the breakpoint functionality. Any >> suggestions? >> > > What kind of breakpoints, hardware-assisted or normal BPs? Are you > trying to break into real-mode code (as stated below - BTW, top-postings > should be avoided!) that happens to run on a non-brand-new Intel host? I > never fully tested how well guest debugging works if KVM has to emulate > instructions, and I wouldn't be surprised if there are "limitations". > > Jan > > >> Jan Kiszka wrote: >> >>> Hi Nicholas, >>> >>> please don't drop CCs on reply. >>> >>> Nicholas Amon wrote: >>> >>> >>>> Hi Jan, >>>> >>>> Thanks for responding. Yes, I am able to step instruction when I >>>> disable kvm w/ the no-kvm option. My host kernel is 64bit 2.6.27 and >>>> the program that I am debugging is 32 bit but starts in real mode. But >>>> the KVM module I am running is from kvm-88. Is there anyway I can check >>>> the version definitively? >>>> >>>> >>> kvm modules issue a message when being loaded, check your kernel log. >>> qemu-kvm gives you the version via -version. >>> >>> OK, the problems you see is likely related to the very old versions you >>> use. Update to recent kvm-kmod (2.6.32 series) and qemu-kvm (0.12 >>> series) and retry. >>> >>> Jan >>> >>> >>> >>>> Thanks, >>>> >>>> Nicholas >>>> >>>> Jan Kiszka wrote: >>>> >>>> >>>>> Jan Kiszka wrote: >>>>> >>>>> >>>>> >>>>>> Nicholas Amon wrote: >>>>>> >>>>>> >>>>>> >>>>>>> Hi All, >>>>>>> >>>>>>> I am trying to single-step through my kernel using qemu and kvm. I have >>>>>>> run qemu via: qemu-system-x86_64 -s -S -hda >>>>>>> /home/nickamon/lab1/obj/kernel.img and also connected to the process >>>>>>> using gdb. >>>>>>> >>>>>>> Problem is that whenever I try and step instruction, it seems to resume >>>>>>> my kernel rather than allowing me to progress instruction by >>>>>>> instruction. I have built the kvm snapshot from git and still no luck. >>>>>>> Tried following the code for a few hours and have no luck. Any >>>>>>> suggestions? >>>>>>> >>>>>>> >>>>>>> >>>>>> What's you host kernel or kvm-kmod version? >>>>>> >>>>>> >>>>>> >>>>>> >>>>> ...and does -no-kvm make any difference (except that it's much slower)? >>>>> >>>>> Jan >>>>> >>>>> >>>>> >>>>> > > My apologies for the late response. Normal breakpoints and yes I am breaking in real mode. This isn't a big issue for me since I am able to break when I disable kvm. So basically I disable kvm when I want to debug and enable it during normal execution. Thanks for all your help. Nick Nicholas Amon See How to Control & Track High-Risk Users: Join our Webinar on Tuesday, June 2 Network World Names Xceedium GateKeeper "RSA 2009 Best of Show"