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From: Markus Armbruster <armbru@redhat.com>
Subject: Re: [Qemu-devel] Re: [libvirt] Supporting hypervisor specific APIs in
	libvirt
References: <4BA7C40C.2040505@codemonkey.ws>
	<201003241230.58160.paul@codesourcery.com>
	<4BAA06E0.5040004@redhat.com>
	<201003241303.25813.paul@codesourcery.com>
Date: Wed, 24 Mar 2010 16:55:30 +0100
In-Reply-To: <201003241303.25813.paul@codesourcery.com> (Paul Brook's message
	of "Wed, 24 Mar 2010 13:03:25 +0000")
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To: Paul Brook <paul@codesourcery.com>
Cc: "libvir-list@redhat.com" <libvir-list@redhat.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>

Paul Brook <paul@codesourcery.com> writes:

>> > IMO the no_user flag is a bug, and should not exist.
>> 
>> Sorry, what's that?
>
> Usually an indication that a device has been incorrectly or inproperly 
> converted to the qdev interface.

Can also be an indication that the device can't support multiple
instances.  For instance:

    commit 39a51dfda835a75c0ebbfd92705b96e4de77f795
    Author: Markus Armbruster <armbru@redhat.com>
    Date:   Tue Oct 27 13:52:13 2009 +0100

        qdev: Tag isa-fdc, PIIX3 IDE and PIIX4 IDE as no-user

        These devices are created automatically, and attempting to create
        another one with -device fails with "qemu: hardware error:
        register_ioport_write: invalid opaque".

        Signed-off-by: Markus Armbruster <armbru@redhat.com>
        Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

With no-user, we at least fail with a decent error message.

I don't think it's fair to demand that a qdev conversion must relax
restrictions that haven't otherwise bothered us to be correct and
proper.  We'll relax them if and when they bother us enough to make
somebody send a decent patch.

And yes, there are better ways to disallow multiple instances of a
device than declaring it no-user.  Patches welcome.