|
From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device to save/restore its state |
Date: | Wed, 19 Jan 2011 11:43:23 -0600 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.15) Gecko/20101027 Lightning/1.0b1 Thunderbird/3.0.10 |
On 01/19/2011 11:19 AM, Daniel P. Berrange wrote:
In our past experiance though, *not* specifying attributes like these has also been pretty bad from a forward compatibility perspective too. We're kind of damned either way, so on balance we decided we'd specify every attribute in qdev that's related to unique identification of devices& their inter-relationships. By strictly locking down the topology we were defining, we ought to have a more stable ABI in face of future changes. I accept this might not always work out, so we may have to adjust things over time still. Predicting the future is hard :-)
There are two distinct things here:1) creating exactly the same virtual machine (like for migration) given a newer version of QEMU
2) creating a reasonably similar virtual machine given a newer version of QEMU
For (1), you cannot use -M pc. You should use things like bus=X,addr=Y much better is for QEMU to dump a device file and to just reuse that instead of guessing what you need.
For (2), you cannot use bus=X,addr=Y because it makes assumptions about the PCI topology which may change in newer -M pc's.
I think libvirt needs to treat this two scenarios differently to support forwards compatibility.
Regards, Anthony Liguori
Daniel
[Prev in Thread] | Current Thread | [Next in Thread] |