Re: [Qemu-devel] [PATCH] move 'unsafe' to end of caching modes in help

[Anthony Liguori <anthony@codemonkey.ws>]

On 07/21/2010 04:58 PM, Daniel P. Berrange wrote:
>> Yes there is.  Use the version number.
>>      
> The version number is not suitable, because features can be removed at
> compile time and/or

I don't see any features that libvirt would need to know about that are 
disabled at compile time that aren't disabled by platform features (i.e. 
being on a Linux vs. Windows host).

>   added via patch backports.

If a distro backports a feature, it should change the QEMU version 
string.  If it doesn't, that's a distro problem.

>   The only reliable way is
> to query the QEMU binary to ask it what it actually supports.
>    

And you do that by asking QEMU what it's version number is.  If the 
version number isn't reliable because a distro backported features 
without changing it, then the distro is broken.  It's no different than 
if we had a capabilities system and a distro added a feature without 
adjusting the advertises capabilities.

Regards,

Anthony Liguori

> Regards,
> Daniel
>