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Re: [Qemu-devel] [PATCH v9 0/5] Extend virtio-balloon for fast (de)infla
Michael S. Tsirkin
Re: [Qemu-devel] [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration
Fri, 14 Apr 2017 04:50:48 +0300
On Thu, Apr 13, 2017 at 01:44:11PM -0700, Matthew Wilcox wrote:
> On Thu, Apr 13, 2017 at 05:35:03PM +0800, Wei Wang wrote:
> > 2) transfer the guest unused pages to the host so that they
> > can be skipped to migrate in live migration.
> I don't understand this second bit. You leave the pages on the free list,
> and tell the host they're free. What's preventing somebody else from
> allocating them and using them for something? Is the guest semi-frozen
> at this point with just enough of it running to ask the balloon driver
> to do things?
There's missing documentation here.
The way things actually work is host sends to guest
a request for unused pages and then write-protects all memory.
So guest isn't frozen but any changes will be detected by host.
Re: [Qemu-devel] [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration, Matthew Wilcox, 2017/04/13
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS, (continued)