* When QEMU encounters a "disk full" condition on the host filesystem,

its default behaviour is to stop the emulator (i.e. suspend the VM).
  For automated tests, this is bad, because is makes the VM appear to
  hang without any error message.  The "werror=report" flag causes
  QEMU to report the problem to the VM.  As a side effect QEMU exits
  very elegantly:

    [    2.308668] end_request: I/O error, dev vda, sector 534400
    [    2.309611] Buffer I/O error on device vda, logical block 66800
    ...
    *** glibc detected *** /nix/store/yhngqrww53j0aw7z7v4bv948x5g5fc3d-qemu-kvm-0.12.1.2/bin/qemu-system-x86_64: double free or corruption (!prev): 0x08e3e040 ***
    Aborted

  So I guess we now depend on a bug in QEMU :-)

svn path=/nixos/trunk/; revision=19703

lib/test-driver/Machine.pm

@@ -25,7 +25,7 @@ sub new {
         $startCommand =
             "qemu-system-x86_64 -m 384 -no-kvm-irqchip " .
             "-net nic,model=virtio -net user \$QEMU_OPTS ";
-        $startCommand .= "-drive file=" . Cwd::abs_path($args->{hda}) . ",if=virtio,boot=on "
+        $startCommand .= "-drive file=" . Cwd::abs_path($args->{hda}) . ",if=virtio,boot=on,werror=report "
             if defined $args->{hda};
         $startCommand .= "-cdrom $args->{cdrom} "
             if defined $args->{cdrom};

modules/virtualisation/qemu-vm.nix

@@ -86,7 +86,7 @@ let
       exec ${pkgs.qemu_kvm}/bin/qemu-system-x86_64 -m ${toString config.virtualisation.memorySize} \
           -no-kvm-irqchip \
           -net nic,model=virtio -net user -smb / \
-          -drive file=$NIX_DISK_IMAGE,if=virtio,boot=on \
+          -drive file=$NIX_DISK_IMAGE,if=virtio,boot=on,werror=report \
           -kernel ${config.system.build.toplevel}/kernel \
           -initrd ${config.system.build.toplevel}/initrd \
           ${qemuGraphics} \