Re: Small changes to libxc (save/restore part 4)

[Jed Davis <jdev%panix.com@localhost>]

Manuel Bouyer <bouyer%antioche.eu.org@localhost> writes:

> On Thu, Sep 08, 2005 at 12:55:53AM -0400, Jed Davis wrote:
>> Save/restore of a NetBSD domU would be nicer, but I'm not there
>> yet.
>
> I've not looked at this in details yet. It shouldn't need much for a domU
> that doens't have access to physical devices. A domU with physical devices
> would probably require to save/restore the device's setups, which probably
> requires a MI framework (not much different from what is needed for e.g.
> ACPI suspend/resume).

With no physical devices: I have looked at the details, or rather at
Linux's implementation of them, and I don't yet understand how to
translate: all of irq_suspend() and irq_resume(), parts of
time_resume(), and what needs to be done to fix up the phys-to-mach
map afterwards.  More staring at code might make this clearer.  The
rest of it seems to be a SMOP.

With physical devices, I don't see Linux trying to do anything about
them, which may just mean that nobody ever tried save/restore/migrate
in that case.

> For live migration, I don't know if there is additionnal support
> needed on the domU's side, or if the hypervisor does all the extra work
> (from what I remember, for a live migration, the domU's memory is copyed
> while the domU's kernel is still running. Then the domU is suspended and
> only pages that have been changed are transfered again).

That's all in the hypervisor and xfrd, from what I've seen of it; the
underlying functionality looked to be related to that used for shadow
page tables.

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