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Message-ID: <4A37C82B.5030805@codemonkey.ws>
Date: Tue, 16 Jun 2009 11:28:27 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] Regression opening read-only cdroms
References: <4A37896C.8050208@redhat.com>	<20090616143259.GA29040@shareable.org>	<4A37B23F.6040604@eu.citrix.com>
	<20090616145421.GD29040@shareable.org>
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To: Jamie Lokier <jamie@shareable.org>
Cc: Avi Kivity <avi@redhat.com>, Christoph Hellwig <hch@lst.de>, qemu-devel <qemu-devel@nongnu.org>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>

Jamie Lokier wrote:
>> 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".
>   

It only is useful if we can expose that read-only attribute to the 
guest.  You can't do that consistently with all block devices so the 
result would be that you'll fail write operations causing a guest to crash.

This is not friendly to a user who expects that ro would Just Work.

Regards,

Anthony Liguori

> -- Jamie
>
>
>