[Qemu-devel] Re: [PATCH v2 3/7] docs: Add QED image format specification

[Avi Kivity]

 On 10/11/2010 04:06 PM, Stefan Hajnoczi wrote:
> On Mon, Oct 11, 2010 at 03:44:38PM +0200, Avi Kivity wrote:
> >   On 10/11/2010 03:42 PM, Stefan Hajnoczi wrote:
> >  >>
> >  >>   A leak is acceptable (it won't grow; it's just an unused, incorrect
> >  >>   freelist), but data corruption is not.
> >  >
> >  >The alternative is for the freelist to be a non-compat feature bit.
> >  >That means older QEMU binaries cannot use a QED image that has enabled
> >  >the freelist.
> >
> >  For this one feature.  What about others?
>
> Compat features that need to be in sync with the image state will either
> require specific checks (e.g. checksum or shadow of the state) or they
> need to be non-compat features and are not backwards compatible.
>
> I'm not opposing autoclear feature bits themselves, they are a neat
> idea.  However, they will initially have no users so is this something
> we really want to carry?

Hard to tell in advance.  It seems like a simple feature with potential 
to make our lives easier in the future.

Anything we develop in the next few months can be rolled back into the 
baseline, assuming we declare the format unstable while 0.14 is in 
development, so this is really about post 0.14 features.

--
error compiling committee.c: too many arguments to function