Re: [PATCH v1 2/2] virtio-balloon: disallow postcopy with VIRTIO_BALLOON_F_FREE_PAGE_HINT

[Peter Xu]

On Wed, Jul 07, 2021 at 04:06:55PM +0200, David Hildenbrand wrote:
> As it never worked properly, let's disable it via the postcopy notifier on
> the destination. Trying to set "migrate_set_capability postcopy-ram on"
> on the destination now results in "virtio-balloon: 'free-page-hint' does
> not support postcopy Error: Postcopy is not supported".

Would it be possible to do this in reversed order?  Say, dynamically disable
free-page-hinting if postcopy capability is set when migration starts? Perhaps
it can also be re-enabled automatically when migration completes?

I see postcopy a "functional" feature and free-page-hint a "performance"
feature, from that pov IMHO it's better to not block function for performance.

Thanks,

-- 
Peter Xu