On Wed, Sep 09, 2026 at 08:30:05AM +0200, Markus Armbruster wrote:
> Michael Roth <[email protected]> writes:
>
> > When in-place conversion is enabled, both the shared memory and private
> > memory must come from the same guest_memfd instance. Thus, the
> > memory-backend-memfd options must in turn correspond to a guest_memfd
> > instance, e.g. guest-memfd=on must be specified. Since there is no
> > use-case for enabling in-place conversion without setting
> > guest-memfd=on, just set it automatically if in-place conversion is
> > enabled.
> >
> > Signed-off-by: Michael Roth <[email protected]>
>
> [...]
>
> > diff --git a/qapi/qom.json b/qapi/qom.json
> > index 20d6fefb04..32df7cb794 100644
> > --- a/qapi/qom.json
> > +++ b/qapi/qom.json
> > @@ -772,7 +772,8 @@
> > # resizing of the memory (default: true)
> > #
> > # @guest-memfd: if true, use guest-memfd to back the memory region.
> > -# (default: false, since: 11.2)
> > +# (default: true for Confidential VMs with in-place conversion,
> > +# false otherwise, since: 11.2)
>
> What does "Confidential VMs with in-place conversion" mean exactly?
> Which configuration settings need to be set how?
Will make sure these gets covered in guest-memfd.rst as well so it can be
referenced here.
>
> > #
> > # Since: 2.12
> > ##
> > @@ -781,7 +782,7 @@
> > 'data': { '*hugetlb': 'bool',
> > '*hugetlbsize': 'size',
> > '*seal': 'bool',
> > - '*guest-memfd': 'bool' },
> > + '*guest-memfd': 'OnOffAuto' },
>
> Valid values change from JSON true and false to JSON "on", "off", and
> "auto".
>
> If @guest-memfd was already in a release, this would be a compatibility
> break, i.e. a hard "don't". But it isn't, it's in the series this is
> one based on. So it's merely a "either avoid or justify in the commit
> message, and avoiding feels easier to me."
Sorry, didn't mean for there to be potential ABI breakage here, I was somehow
under the impression that OnOffAuto accepted 'true'/'false' as a backward
compatibility mechanism, but that's clearly not the case.
I'll plan to switch to OnOffAuto in Peter's series so it's defined that
way from the start.
Thanks,
Mike
>
> The doc comment still uses true and false.
>
> > 'if': 'CONFIG_LINUX' }
> >
> > ##
>
