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

[Anthony Liguori <anthony@codemonkey.ws>]

On 07/21/2010 04:32 PM, Daniel P. Berrange wrote:
> On Wed, Jul 21, 2010 at 03:55:28PM -0500, Anthony Liguori wrote:
>    
>> On 07/21/2010 03:32 PM, Bruce Rogers wrote:
>>      
>>> Libvirt parses qemu help output to determine qemu features. In particular
>>>   it probes for the following: "cache=writethrough|writeback|none". The
>>>   addition of the unsafe cache mode was inserted within this string, as
>>>   opposed to being added to the end, which impacted libvirt's probe.
>>>   Unbreak libvirt by keeping the existing cache modes intact and add
>>>   unsafe to the end.
>>>
>>> This problem only manifests itself if a caching mode is explicitly
>>> specified in the libvirt xml, in which case older syntax for caching is
>>> passed to qemu, which it  no longer understands.
>>>
>>> Signed-off-by: Bruce Rogers<brogers@novell.com>
>>>
>>>        
>> Errr, libvirt is still doing this?
>>
>> This comes up frequently and it's a real PITA.  Help text is not a
>> feature probing interface.  This is a libvirt bug and it needs to be
>> fixed in libvirt
>>      
> Of course, there is no viable alternative yet.

Yes there is.  Use the version number.

Regards,

Anthony Liguori

>   The QMP patches I
> sent a few weeks back now to add ability to query capabilities were
> intended to provide the neccessary support in QEMU for us to use
> instead of -help. Given that QMP isn't going to be declared stable
> in 0.13 though, it looks like we'll be continuing to use -help
> until the 0.14 release of QEMU.
>
>
> Regards,
> Daniel
>