Re: [Xen-devel] RFC: Making QEMU honour 'readonly' flag for disks

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Wed, Jul 30, 2008 at 10:01:29AM +0100, Ian Jackson wrote:
> Daniel P. Berrange writes ("[Xen-devel] RFC: Making QEMU honour 'readonly' 
> flag for disks"):
> > The Xen disk configuration syntax allows a block device to be marked as
> > readonly, exclusive writable or shared writeable. The xen hotplug scripts
> > will clash for clashing configs between domains, but  it is upto the
> > backend drivers to actually enforce the readonly flag on I/O operations.
> > The paravirt backend disk driver does this fine, but QEMU's emulated
> > backend driver does not.
> 
> I still think this is a fix we should have but your patch is very
> intrusive.  Is there some reason why you didn't just invent
> BDRV_O_RDONLY_NO__ACTUALLY__READONLY ?  A new parameter to bdrv_new
> seems quite wrong.
> 
> (It's a shame that the existing BDRV_O_RDONLY does something strange
> and probably wrong, but we probably don't want to fix that in our
> branch.)

Yeah, I'm actually attempting to fix that craziness, which is why
I've not posted an update yet. I think it may actually be easier
to fix that it appears....

Daniel
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