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Date: Mon, 26 Jul 2010 22:43:58 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] move 'unsafe' to end of caching modes in help
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, Bruce Rogers <brogers@novell.com>

  On 07/26/2010 10:35 PM, Anthony Liguori wrote:
>
>>
>>>> If you want libvirt to do the right thing, provide a proper 
>>>> capabilities interface.  Using the version has its downsides as 
>>>> much as the help text.
>>>
>>> That's simply not the case.  Please, provide an actual example where 
>>> version is not reliable and backports aren't trivially easy to detect.
>>
>>
>> t=0 starting point, cache=unsafe is unknown
>> t=1 qemu upstream adds cache=unknown
>> t=2 libvirt adds support for cache=unsafe, releases
>> t=3 evil distro backports cache=unsafe, releases qemu-kvm-1.2.3.4
>> t=4 user tries libvirt from t=2 with qemu from t=3, cache=unsafe not 
>> detected
>>
>> version numbers force a libvirt update every time a feature is 
>> backported.
>
> That's a bogus scenario because said evil distro would also enhance 
> libvirt to detect the feature properly.

That means a new libvirt release is needed.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.