Re: [Xen-devel] Shutdown of HVM domains without PC drivers [was Re: Early ACPI events prevent subsequent ACPI functionality on xen 4.3 + HVM domU]

[Alex Bligh <alex@xxxxxxxxxxx>]

Sander,

--On 27 June 2013 19:15:22 +0200 Sander Eikelenboom <linux@xxxxxxxxxxxxxx> 
wrote:
> > > On 21/05/13 18:31, Sander Eikelenboom wrote:
> > >
> > > > This reminds me that there still is the issue that a HVM domain without
> > > > PV drivers doesn't shutdown properly with the standard init.d scripts.
> > > BTW, if you want this to get attention, you should probably either reply
> > > to that thread, or start a new thread.  Starting a new topic on an
> > > unrelated thread is generally frowned upon. :-)
> > Something needs to tell the guest to shut down. Without pvdrivers, you'll
> > need to do it through ACPI. Do you have ACPI installed, and are you
> > sending an xl power event?
>
> Hi Alex/George,
>
> The problem is NOT with a manual sent command by a admin, who has both
> knowledge and can (directly) respond to warning that is issued (although
> it's a bit harder in the --all case).
>
> It's with automated scripts using "xl shutdown [-a]", in combination with
> HVM guests which do not have PV drivers installed.
Yes I know. We have this problem.

xl shutdown and friends only send the PV signals (I believe). As your
guest has no PV drivers, I believe this will do nothing (xl might wait
for a timeout and destroy)

You can use the xl power events to send ACPI signals to shutdown guests
without PV drivers. This also works for guests with PV drivers if they
have ACPI in.

So, the way we get round this is not to use the xl commands (well, libxl
calls in our case) that use the PV interface at all. We simply use
the ACPI stuff (the power events), which works whether or not the guest
has PV support. This requires the guest to have ACPI installed for a clean
shutdown, which is exactly the same requirement for KVM, and hence works
well.

We have found (for various reasons) it may be necessary to send the
power event multiple times until something happens, rather than simply
wait for a timeout.

If a shutdown is used, and you send it to early in the boot process,
then subsequent shutdowns may not work - I reported a bug on that
(it's somewhere on the not-for-4.3 list). This in my book another
reason to avoid xl shutdown and use the power events instead. The
only disadvantage of this strategy is if you have guests which have
PV drivers but not ACPI; these tend to be machines built for PV rather
than HVM, being run on HVM (e.g. AMIs someone has stuck a kernel
in and hoped for the best).

--
Alex Bligh

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