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Re: [libvirt] [Qemu-devel] [PATCH RFC 0/4] Allow hibernation on guests



On 01/26/2012 09:18 AM, Eric Blake wrote:
[adding qemu-devel]

On 01/26/2012 07:46 AM, Daniel P. Berrange wrote:
One thing, that you'll probably notice is this
'set-support-level' command. Basically, it tells GA what qemu version
is it running on. Ideally, this should be done as soon as
GA starts up. However, that cannot be determined from outside
world as GA doesn't emit any events yet.
Ideally^2 this command should be left out as it should be qemu
who tells its own agent this kind of information.
Anyway, I was going to call this command in qemuProcess{Startup,
Reconnect,Attach}, but it won't work. We need to un-pause guest CPUs
so guest can boot and start GA, but that implies returning from qemuProcess*.

So I am setting this just before 'guest-suspend' command, as
there is one more thing about GA. It is unable to remember anything
upon its restart (GA process). Which has BTW show flaw
in our current code with FS freeze&  thaw. If we freeze guest
FS, and somebody restart GA, the simple FS Thaw will not succeed as
GA thinks FS are not frozen. But that's a different cup of tea.

We could drop the state tracking (guest-fsfreeze-status) and issue the freeze/thaw unconditionally. Talked with Anthony and going stateless in general seems to solve a lot of nastiness that might pop up with the current implementation. I'll send some patches out soon for fsfreeze, guest-file* may end up getting similar treatment in the not-too-distant-future.


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