Re: [Qemu-devel] [libvirt] [PATCH v2] deprecate -mem-path fallback to anonymous RAM

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jun 25, 2019 at 01:18:01PM -0500, Eric Blake wrote:
> On 6/25/19 11:16 AM, Igor Mammedov wrote:
> > Fallback might affect guest or worse whole host performance
> > or functionality if backing file were used to share guest RAM
> > with another process.
> > 
> > Patch deprecates fallback so that we could remove it in future
> > and ensure that QEMU will provide expected behavior and fail if
> > it can't use user provided backing file.
> > 
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> > v2:
> >  * improve text language
> >     (Markus Armbruster <armbru@redhat.com>)
> > 
> 
> Is this deprecation introspectible? Does it need to be?
> 
> Do we even need a deprecation period, or can we declare this a bug fix
> (it was a bug that we didn't fail outright on an impossible request) and
> do it immediately?

I think it is hard to call it a bug when we added explicit extra code to
make it work as it does today.

It is really a misguided feature.

> If it is not a bug fix, perhaps it could be made introspectible by
> having a new boolean parameter to opt in to the failure now, rather than
> 2 releases from now?

From libvirt's POV I don't see a need for introspection. There's no
special action we need to take to deal with the new behaviour - it is
ultimately just providing the behaviour we kind of assumed it already
had.


Regards,
Daniel
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