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From: Laurent Vivier <Laurent@vivier.eu>
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Date: Sun, 04 Mar 2012 01:44:23 +0100
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Subject: [Qemu-devel] NBD broken ?
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To: qemu-devel@nongnu.org
Cc: Paolo Bonzini <pbonzini@redhat.com>

Hi,

since commit ae255e523, qemu with NBD hangs at startup (when it tries to
access the disk):

commit ae255e523c256cf0708f1c16cb946ff96340a800
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Thu Sep 8 14:28:59 2011 +0200

    nbd: switch to asynchronous operation
    
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>


Reverting this patch corrects the problem.

My system is an Ubuntu 11.04 x86_64 (But the bug is also seen on RHEL6).

qemu is configured only with "--target-list=x86_64-softmmu".

My test case is:

./qemu-nbd -k /tmp/nbd-socket -t /ISO/ubuntu-11.04-desktop-i386.iso

./x86_64-softmmu/qemu-system-x86_64 -cdrom nbd:unix:/tmp/nbd-socket

Same problem with a TCP socket, with/without KVM, with an x86_64 guest, with -hda...
 
Regards,
Laurent