Re: [PATCH 10/13] virtio_balloon: add higher-order page inflation

[Kevin Loughlin]

On Wed, Oct 28, 2026 at 1:59 AM David Hildenbrand (Arm)
<david@xxxxxxxxxx> wrote:
>
> On 10/27/26 03:56, Kevin Loughlin wrote:
> > In confidential computing guests requiring page state transitions,
> > unaccepted memory tracking operates at the EFI unaccepted memory unit
> > granularity (typically 2MB / order 9 on x86). Inflating the balloon
> > with 4KB pages would prevent unaccepting the backing 2MB unit.
> >
> > Inflate balloon pages at unaccepted_memory_order() when
> > virtballoon_cc_needs_state_transition() is true, while retaining
> > order-0 allocations for non-CoCo guests and CoCo guests that do not
> > use unaccepted memory transitions. When a higher-order balloon page
> > spans more 4KB balloon PFNs than VIRTIO_BALLOON_ARRAY_PFNS_MAX (256),
> > transmit its PFNs to the host in VIRTIO_BALLOON_ARRAY_PFNS_MAX chunks.
> >
> > Signed-off-by: Kevin Loughlin <kevinloughlin@xxxxxxxxxx>
>
> Sorry, not happening. There is no migration support for these (large) things,
> and there likely won't be any time soon.
>
> NAK

Yeah, you're right. Another great reason to abandon the
inflate/deflate aspect of this series beyond what Michael pointed out.
I will follow up on the cover letter RE: how doing so might provide a
path forward for the CoCo free page reporting by simplifying things.