[Qemu-devel] [Bug 1027525] Re: Unable to insert cd media located on ro nfs mount

[Kevin Shanahan]

Looks like the read_only flag in the block device state never gets set.
This needs to be set otherwise qmp_change_blockdev tries to open the
device read only. This patch works for me.

** Patch added: "Proposed fix"
   
https://bugs.launchpad.net/qemu/+bug/1027525/+attachment/3245422/+files/cdroms-are-read-only.patch

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https://bugs.launchpad.net/bugs/1027525

Title:
  Unable to insert cd media located on ro nfs mount

Status in QEMU:
  New

Bug description:
  When issuing a "change" command via the monitor, qemu is unable to
  open the iso file if it is mounted on a read-only nfs share. If I
  mount read-write (and make sure the file is writable by the qemu
  process), then the change command succeeds. Note that this doesn't
  affect media specified on the command line when starting qemu, only
  when changing via the monitor.

  To reproduce, mount cd images directory read only, e.g.

  address@hidden ~]# grep iso /etc/fstab
  10.48.50.20:/iso /srv/kvm/iso nfs4 defaults,ro 0 0

  Start qemu with minimal options, just need access to the monitor:

  address@hidden ~]# kvm -vnc 127.0.0.1:0 -S

  Connect to the monitor and issue a change command:

  (qemu) change ide1-cd0 /srv/kvm/iso/ubuntu-12.04-server-amd64.iso
  Could not open '/srv/kvm/iso/ubuntu-12.04-server-amd64.iso

  Re-mount the iso directory read-write and notice that the command
  succeeds:

  address@hidden ~]# mount -o remount,rw /srv/kvm/iso

  (qemu) change ide1-cd0 /srv/kvm/iso/ubuntu-12.04-server-amd64.iso
  (qemu)

  address@hidden ~]# kvm --version
  QEMU emulator version 1.1.1 (qemu-kvm-1.1.1), Copyright (c) 2003-2008 Fabrice 
Bellard
  address@hidden ~]# uname -a
  Linux kvmhost0 3.4.5-1-ARCH #1 SMP PREEMPT Mon Jul 16 21:35:54 CEST 2012 
x86_64 GNU/Linux

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