From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41598) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YGsFh-00040g-7m for qemu-devel@nongnu.org; Thu, 29 Jan 2015 11:47:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YGsFb-0006vA-Ng for qemu-devel@nongnu.org; Thu, 29 Jan 2015 11:47:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36496) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YGsFb-0006uc-Fy for qemu-devel@nongnu.org; Thu, 29 Jan 2015 11:47:27 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t0TGlPHk026393 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Thu, 29 Jan 2015 11:47:26 -0500 Date: Thu, 29 Jan 2015 16:47:23 +0000 From: "Richard W.M. Jones" Message-ID: <20150129164723.GA3860@redhat.com> References: <20150129162509.GA32706@tesla.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150129162509.GA32706@tesla.redhat.com> Subject: Re: [Qemu-devel] QEMU segfault: Booting an overlay with backing_file over NBD: nbd.c:nbd_receive_request():L756: read failed List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kashyap Chamarthy Cc: qemu-devel@nongnu.org On Thu, Jan 29, 2015 at 05:25:09PM +0100, Kashyap Chamarthy wrote: > A simple reproducer below. > > Export a disk image over NBD (I realize port 10809 is default, thought > I'd explicitly mention anyhow): > > $ qemu-nbd --f qcow2 -p10809 \ > /var/lib/libvirt/images/cirros-0.3.3-x86_64-disk.img -t > > > Create an overlay with backing file exported via NBD: > > $ qemu-img create -f qcow2 -F \ > nbd -o backing_file=nbd://localhost overlay1.qcow2 > Formatting 'overlay1.qcow2', fmt=qcow2 size=41126400 backing_file='nbd://localhost' backing_fmt='nbd' encryption=off cluster_size=65536 lazy_refcounts=off > > > Let's attempt to boot the overlay with a minimal QEMU: > > $ qemu-system-x86_64 \ > -nographic \ > -nodefconfig \ > -nodefaults \ > -m 2048 \ > -device virtio-scsi-pci,id=scsi \ > -device virtio-serial-pci \ > -serial stdio \ > -drive file=./overlay1.qcow2,format=qcow2,if=virtio,cache=writeback > Segmentation fault (core dumped) > > > On the shell where `qemu-nbd` is running, I notice this > > nbd.c:nbd_receive_request():L756: read failed This is a "normal error" -- it just means the client dropped the connection. You really need to get the stack trace from that core dump to debug this further. Rich. > Haven't investigated further with GDB, thought I'd bring it up here > first. > > > Versions > -------- > > $ rpm -q qemu; uname -r > qemu-2.1.2-7.fc21.x86_64 > 3.17.8-300.fc21.x86_64 > > -- > /kashyap -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW