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Re: [Xen-devel] Domain save/migrate issue

Noam Taich wrote:
We need the memory image of the domain to be static, So we can't allow
the domain to run. So, the first idea is to use pause/unpause instead of
Suspend does more than just canonicalize the p2m, it also provides callbacks for all of the devices so that they can canonicalize their own page references and set them self up to reinitialize upon resume.

While the save code can access the p2m table, it has no way of knowing the device information so just pausing isn't really an option (also, you could do bad things like checkpoint before a storage operation was committed or something like that).


Anthony Liguori

Now for the next (serious) problem:
This seems to work fine (in live or non live settings) until the
xc_linux_save() function reaches the part where it checks the frame
Of the suspend record, which makes sense, because now, we have NO
suspend record. So, the second idea is to (simply?) write all that info
on the io_fd
The function gets ourselves. Just canonicalize the fns that suspend
And write the appropriate info.

The restore function does not have to change at all... it sees the same

So, what do you think, is this a good idea? Even possible? Will it
entail a lot?

One of my concerns is this: the shared pages.
Can Xen write to them while the guest is "only" paused? And if so, what Can it (practically) write there while the guest is paused? Even if it CAN, is it Reasonable to expect it won't do that usually?

I'm not really troubled by the storage issues. This feature would be
useful in many cases even with no solution to that problem.

Sorry for the multiple messages on the original subject. It was an
unfortunate misunderstanding.

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