On 04/14/2017 09:50 AM, Michael S. Tsirkin wrote:
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.
Probably it's better to say " transfer the info about the guest unused pages
to the host so that the host gets a chance to skip the transfer of the
unused
pages during live migration".
Best,
Wei
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