Re: [virtio] New virtio balloon...

[Daniel Kiper <daniel.kiper@oracle.com>]

On Tue, Feb 04, 2014 at 12:00:21PM +1030, Rusty Russell wrote:
> "Michael S. Tsirkin" <mst@redhat.com> writes:
> > On Mon, Feb 03, 2014 at 01:37:17PM +1030, Rusty Russell wrote:
> >> "Michael S. Tsirkin" <mst@redhat.com> writes:
> >> > On Fri, Jan 31, 2014 at 04:01:39PM +1030, Rusty Russell wrote:
> >> >> The driver needs to explicitly ask for pages in that region.
> >> >
> >> > OK so we'll have an extra flag for that?
> >>
> >> No, I mean that the driver explicitly requests every page by PFN.  If it
> >> requests a page in the extramem region, it will get one.
> >
> > Maybe I misunderstand. What is EXTRA_MEM is aid of?
>
> The VIRTIO_BALLOON_F_EXTRA_MEM feature enables the extra memory region.
> It's a simple form of memory hotplug.  Daniel wanted it.
>
> It might make sense for some guests to allocate metadata (eg. array of
> struct pages) for that extra memory if it's required.

Linux does this dynamically during memory hotadd phase.

Daniel