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Date: Tue, 08 Jun 2010 10:17:20 -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: Gerd Hoffmann <kraxel@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Glauber Costa <glommer@redhat.com>, qemu-devel@nongnu.org

On 06/08/2010 08:44 AM, Gerd Hoffmann wrote:
> On 06/08/10 15:07, Anthony Liguori wrote:
>>>> 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.
>
> Hmm.  I think qemuopts need to carry information about the option 
> types, whenever it is single-entry or multiple-entry.
>
> Oh, and likewise for the sections.  With multiple (unnamed) [device] 
> sections we want create multiple (id-less) device sections.  With 
> multiple [machine] sections we probably want to merge the options 
> instead.
>
>> Or more specifically:
>>
>> foo.conf:
>>
>> [drive]
>> file=foo.img
>> if=virtio
>> id=bar
>
> This would be '[drive "bar"]' without id= line btw.
>
>> 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.
>
> Or the user's config the global config.
>
> For multi-entry options this will be tricky.  What do you expect to 
> happen here:
>
> global.conf
>   [net "user"]
>     type="slirp"
>     guestfwd=<fw1>
>
> user.conf
>   [net "user"]
>     guestfwd=<fw2>
>     guestfwd=<fw3>
>
> Which forwardings will be active then?  All of them?  Or will the 
> user.conf forwardings override the global one?

What'd expect is:

[net "user"]
guestfwd = <fw1> <fw2> <fw3>..

I think multiple entry options are probably not a good thing to have.

Regards,

Anthony Liguori

> cheers,
>   Gerd
>