On 05/18/2012 08:08 AM, Stefan Hajnoczi wrote:
On Mon, May 7, 2012 at 3:30 PM, Anthony Liguori<anthony@xxxxxxxxxxxxx> wrote:
On 05/06/2012 09:39 AM, Avi Kivity wrote:
On 05/06/2012 05:35 PM, Anthony Liguori wrote:
So what's really the use case here? Would an IPMI -> libvirt bridge get you
what you need? I really think that's the best path forward.
Sorry for sending this twice. I thought my mailer was set to disable HTML.
Many of our customer use the standard watchdog timer and power controls
on IPMI. Basically, the watchdog timer needs to be able to power off,
power cycle, reset, and send an NMI. The IPMI watchdog can be
configured to do all those things. (The NMI is for a "pretimeout" that
generally triggers a panic.)
Power control is no big surprise. It's true that you have ACPI to do
this, but that's not terribly useful on non-x86 (and non ia64, I
suppose) systems.
Do you want to expose host sensors - the challenge is that they don't
reflect the hardware that the virtual machine sees? Or do you want to
have synthetic sensors - which virtual sensors are useful to have?
A few sensors, notably the watchdog timer sensor, are not synthetic.
The others generally are. Sensors cover things beyond just power and
temperature. Important other ones in IPMI deal with the presence of
FRUs in the system, BIOS/OS state, and intrusion detection.
Two main reasons for synthesized sensors exist. One, in a legacy
situation, is to "fool" the management system into thinking everything
is ok, since it is expecting to see these sensors with specific values.
You could even possibly reflect the state of real sensors, mapping them
somehow, if you wanted.
The other reason is for testing. It's pretty hard to induce some of
these sensors to go out of range in a real system. So without
simulation, you need a hack-ed up management controller in a real system
to truly test your software.
Is the IPMI watchdog useful, QEMU already supports the i6300esb PCI
watchdog (see qemu -watchdog option documentation)?
That's only useful if you can simulate an i6300esb. Probably not
possible on non-x86. Plus legacy systems may be expecting the
capabilities of the IPMI watchdog.
Some use cases that illustrate how the guest is going to use IPMI
would be interesting and could help guide the discussion.
You are probably right. I've mentioned a couple above.
One other possible one, that someone else mentioned, is the ability to
control a VM using standard tools like ipmitool or OpenIPMI over network
interfaces. People may already have management systems that are
designed around IPMI, and it would make a move to virtual machines
easier. This was the request mentioned that was in the Redhat database.
Such a capability would require re-thinking things a bit. You have two
basic options that I see. Either have the "management controller" run
outside qemu and define a simple interface to it, or modify qemu to be
able to run the management controller internally.
My preference in to run it outside qemu, for the following reasons:
* It decouples things that are IPMI internals from having to go
through getting into qemu repositories.
* The management controller then becomes useful for a number of other
purposes. I already have one mostly done that I use for testing.
It could be used by other VMs.
* A full management controller is a fairly big piece of software,
especially if you include the network access. It probably doesn't
belong in qemu.
* No offense, I don't want to muck around inside qemu to accomplish
this :).
There are, of course, disadvantages. Some I can think of:
* There can be confusion about which versions of two things work together.
* Overall, it is more complex to get working.
* There are possible security implications.
So I guess those are points we can talk about...
-corey
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