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Date: Tue, 08 Jun 2010 08:07:34 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] Re: [PATCH 01/22] QemuOpts: fix a bug in QemuOpts
	when setting an option twice
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Glauber Costa <glommer@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>, qemu-devel@nongnu.org

On 06/08/2010 05:32 AM, Paolo Bonzini wrote:
> On 06/08/2010 09:51 AM, Gerd Hoffmann wrote:
>> On 06/08/10 01:51, Anthony Liguori wrote:
>>> Right now, if you set a QemuOpts option in a section twice, when
>>> you get the option you'll receive the value that was set the first
>>> time. This is less than ideal because if you're manipulating
>>> options in two places like a global config followed by the command
>>> line, you really want the later to override the former.
>>>
>>> This patch fixes this behavior.
>>
>> Note that this reverses the ordering for users which want multiple
>> values (slirp forwarding for example).
>
> And qemu_opt_find seems to have thought about this too:
>
> static QemuOpt *qemu_opt_find(QemuOpts *opts, const char *name)
> {
>     QemuOpt *opt;
>
>     QTAILQ_FOREACH_REVERSE(opt, &opts->head, QemuOptHead, next) {
>         if (strcmp(opt->name, name) != 0)
>             continue;
>         return opt;
>     }
>     return NULL;
> }
>
> Can you show the behavior with commandline arguments only?

The problem I was trying to address can be seen with something like:

-drive file=foo.img,if=virtio,file=bar.img

You get no error, and foo.img is what gets used.  It's fair to argue 
this is a silly use case but what I'm trying to achieve is to make it 
possible to do:

-drive file=foo.img,if=virtio,id=bar -drive file=bar.img,id=bar

Or more specifically:

foo.conf:

[drive]
   file=foo.img
   if=virtio
   id=bar

qemu -readconfig foo.conf -drive file=bar.img,id=bar

IMHO, what's specified next on the command line ought to override what's 
in the config.

Suggestions how to achieve this in a more elegant way would be appreciated.

Regards,

Anthony Liguori

> Paolo
>