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Re: [Qemu-devel] QEMU segfault: Booting an overlay with backing_file ove
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] QEMU segfault: Booting an overlay with backing_file over NBD: nbd.c:nbd_receive_request():L756: read failed |
Date: |
Thu, 29 Jan 2015 16:47:23 +0000 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
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
--
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