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]

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Thursday, June 27, 2013, 9:31:53 PM, you wrote:

> 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).

Well with my little adjustments its working for my situation just fine.
You are right there is still a time window that neither the pv method or the 
acpi method will work (during guest boot).
The only thing that can be done seems to be:

- Retry on intervals, under the assumption that the guest is still booting and 
hope it will get to a point it can be shutdown by either pv or acpi method, and 
timeout and destroy eventually.

The point is, is the current (default) behavior of "xl shutdown" (only try pv 
method) sensible ..
That the Xen automated test system run into this problem seems to suggest it is 
at least debatable.

So it's not a major issue for me, just a tiny nit that people can run into when 
using only xl and the default scripts for domain management.


--
Sander


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