Re: [Xen-devel] Early ACPI events prevent subsequent ACPI functionality on xen 4.3 + HVM domU

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Tuesday, May 21, 2013, 6:09:33 PM, you wrote:

> On 05/21/2013 04:59 PM, Alex Bligh wrote:
>> George,
>>
>> --On 21 May 2013 16:23:00 +0100 George Dunlap
>> <george.dunlap@xxxxxxxxxxxxx> wrote:
>>
>>> On 05/21/2013 04:16 PM, Alex Bligh wrote:
>>>> George,
>>>>
>>>> --On 21 May 2013 14:39:55 +0100 George Dunlap
>>>> <George.Dunlap@xxxxxxxxxxxxx> wrote:
>>>>
>>>>> So this appears to be an xl toolstack thing.  I managed to reproduce
>>>>> your results using "xl shutdown -F [domain]"; but if you then do "xl
>>>>> trigger [domian] power", the domain shuts down as normal.
>>>>
>>>> OK. But doesn't the power thing yank the power rather than send a
>>>> clean shutdown?
>>>
>>> No -- if you push the button just once on most modern hardware it will
>>> send an ACPI "poweroff" event that the OS handles gracefully.  That's
>>> what gets sent when you do "xl trigger [domain] power".  If the OS
>>> ignores it (either on real hardware or virtual hardware) nothing happens.
>>> On real hardware you have to then hold down the button for 5 seconds for
>>> a hard-shutdown, with xl you have to do "xl destroy".
>>
>> OK, great. I am guessing the reason why 'xl shutdown' doesn't do
>> that is to cope with (a) non-HVM domains, and (b) old fashioned
>> HVM domains with PV support but not ACPI support. Correct?
>>
>>>> We are using libxl here (admittedly having looked carefully at
>>>> the xl code for guidance) and get the same problem.
>>>
>>> The relevant xl code is here:
>>>
>>>      rc=libxl_domain_shutdown(ctx, domid);
>>>      if (rc == ERROR_NOPARAVIRT) {
>>>          if (fallback_trigger) {
>>>              fprintf(stderr, "PV control interface not available:"
>>>                      " sending ACPI power button event.\n");
>>>              rc = libxl_send_trigger(ctx, domid, LIBXL_TRIGGER_POWER, 0);
>>>          } else {
>>>              fprintf(stderr, "PV control interface not available:"
>>>                      " external graceful shutdown not possible.\n");
>>>              fprintf(stderr, "Use \"-F\" to fallback to ACPI power
>>> event.\n");
>>>          }
>>>      }
>>>
>>> It looks like libxl_domain_shutdown() will only use the PV shutdown
>>> method.  If that method is not available, then it will call
>>> libxl_send_trigger().
>>
>> OK. Well if that's the case, why is it not working? i.e. how
>> is using 'xl trigger power' a workaround? As our testing was
>> on xl (as well as libxl). Perhaps libxl_domain_shutdown
>> is returning an error other than ERROR_NOPARAVIRT or no error
>> at all?

> xl/libxl is working as designed. xl tried libxl_domain_shutdown() first. 
>   libxl saw that there were PV drivers available, so it sent the PV 
> shutdown signal over xenstore and returned success.  libxl and xl have 
> no way of knowing that the signal was never received, so it never falls 
> back to ACPI.

At a sidenote ...

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.
It was discussed last year with IanC and IanJ, to make the fallback to acpi 
automatical (at present it isn't it just prints a warning)
IanJ was in favor, IanC wasn't convinced that it wouldn't hurt in some cases. 
At some point the discussion resulted in a stalemate.
(thread is here: 
http://lists.xen.org/archives/html/xen-devel/2012-10/msg01973.html )

There are a few options:
- always invoking acpi method if pv method fails in libxl
- add -F to the shutdown line in /etc/(sysconfig|default)/xendomains, so 
automatically invoking the shutdown is only done from the shutdown script.
- adding a option to the domains cfg (f.e. shutdown="shutdown_acpi" instead of 
shutdown="shutdown")

This issue also causes the "guest-stop fail   never pass" results in the auto 
test system.

--
Sander


> "xl trigger power" is a work-around because when you detect that a guest 
> is stuck, you should be able to issue an ACPI shutdown and get a clean 
> shutdown, even when the PV shutdown path is stuck.

> (In fact, as a short-term solution, you might consider just replacing 
> "xl shutdown $d" with "xl trigger $d power" in your control framework.)

>> Does xl trigger reset do the same thing (i.e. a graceful shutdown)?
>> If not we'd also (I think) have to recode reboots to do a power trigger
>> then a restart.

> Hmm, this is what I get:

> # xl trigger h0 reset
> libxl: error: libxl.c:4639:libxl_send_trigger: Send trigger 'reset' 
> failed: Function not implemented

> YMMV...

>   -George




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