Re: [qemu-s390x] [Qemu-devel] [PATCH 3/3] s390x: deprecate s390-squash-mcss machine prop

[Halil Pasic]

On 12/05/2017 03:54 PM, Eric Blake wrote:
> On 12/05/2017 06:05 AM, Halil Pasic wrote:
> 
>> Good catch! Regarding omitting the machine name, I was surprised that
>> it works, but it does. Our documentation is a bit strange on this: we
>> document the machine name as non-optional:
>> "-machine [type=]name[,prop=value[,...]]"
>> but then use -machine prop=value in the deprecation section (that's
>> with no name).
> 
> QemuOpts at their "finest".  If it sees the first hunk as a value
> without an =, then that value is fed to type=name; but you are also free
> to make the first hunk be an explicit name=value (whether type=name or
> prop=value), at which point it is up to the backend whether type can be
> omitted.  So in this case, '-machine prop=value' manages to work just
> fine, and it's a question of how you would convey that information in
> the --help documentation.
> 

I would have spontaneously said something like 
-machine [[type=]name | prop=value][,prop=value,[,...]]

It is kind of complicated and it does not precisely reflect what is possible
(one can specify the machine multiple times, and it does not have to be
a prefix of the list for example) but that ain't necessarily a problem.

I'm not saying we should change this. I just wanted to say: wow, this was
new to me.

>>
>> Since the documentation doesn't make it clear that the property is
>> existent only for the s390-ccw-virtio family of the machines I think
>> being your suggestion has a lot of charm. @Connie: do you agree to
>> removing the machine name (type)?
>>

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