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Date: Tue, 08 Jun 2010 15:44:50 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] Re: [PATCH 01/22] QemuOpts: fix a bug in QemuOpts
	when setting an option twice
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Glauber Costa <glommer@redhat.com>, qemu-devel@nongnu.org

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?

cheers,
   Gerd