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Date: Tue, 16 Jun 2009 15:54:21 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Regression opening read-only cdroms
Message-ID: <20090616145421.GD29040@shareable.org>
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: qemu-devel <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>, Christoph Hellwig <hch@lst.de>

Stefano Stabellini wrote:
> Jamie Lokier wrote:
> 
> > Avi Kivity wrote:
> >> qemu used to be quite happy opening read-only cdrom images, and I was 
> >> quite happy feeding kvm-autotest a library of read-only iso images.
> > 
> > 1. While we're here, an _option_ to open an image read-only even when
> >    you have write permission would be useful, for those occasions when
> >    you want to boot from some valuable image and be certain you aren't
> >    modifying it - without having to chmod back and forth in
> >    Qemu-wrapper scripts, or copy the image first.
> 
> 
> Indeed.
> I have a patch that adds bdrv_set_read_only that set bs->read_only = 1
> so that bdrv_open2 can check if the flag is set and act accordingly.
> The problem is that in xen we read whether the device should be opened
> read only in the VM config file, I don't think the user can specify to
> open a drive read-only in qemu.

What's missing is a "ro" sub-option to "-drive".

-- Jamie