[Xen-devel] Powerdown problem on XEN | ACPI S5

[Atom2 <ariel.atom2@xxxxxxxxxx>]

Hi guys,
I have been liasing with Ian Campbell on the xen-user list and Ian 
suggested I should take this to xen-devel.
The issue I am currently facing is as follows:
I seem to be unable to powerdown my system under the XEN hypervisor by 
issuing the command
        shutdown -h now

from my gentoo-hardened 3.9.5 dom0 machine. Instead of turning off 
power, it goes through a BIOS power-on sequence and reboots. There's no 
other domU running at the time of the attempted powerdown.
If I do the same using *exactly the same dom0 kernel* without XEN 
involved (i.e. boot from my gentoo-hardened 3.9.5 kernel only), 
powerdown reliably works as expected and 'shutdown -h now' turns off the 
system's power.
I have tested both 4.2.2 (the gentoo e-build) and 4.3 (downloaded 
directly from xenbits). There's no difference between those two versions 
in terms of reboot versus powerdown.
Upon advise from Ian I have also experimented with the various reboot= 
options on the command line - also with no success.
Adding a serial console (also thanks to Ian's input) I was able to 
examine the messages during shutdown. I have attached those from 4.2.2 
for your reference.

For the latest test using Xen 4.2.2 I made a few changes to the source 
file xen/arch/x86/acpi/power.c to see where the actual problem may be 
hidden. I'm far from being a kernel or XEN programmer, but I am able to 
read and basically understand and (to an extent) modify C code. 
Supported by finding and identifying the messages I had on the serial 
console I decided to add a few additional printk statements after the 
last message that was displayed on the console to see where the system 
probably crashes / the problems could possibly start:
After my change, the relevant code snippet now looks as follows (NOTE: 
The printk messages starting with "After" or "Before" stem from me, the 
first one and the one within the if-construct are both unchanged; the 
initial one was originally always displayed on the serial console as the 
final line):
    printk("Entering ACPI S%d state.\n", state);

    local_irq_save(flags);
    printk("After local_irq_save\n");

    spin_debug_disable();
    printk("After spin_debug_disable\n");

    if ( (error = device_power_down()) )
    {
        printk(XENLOG_ERR "Some devices failed to power down.");
        system_state = SYS_STATE_resume;
        goto done;
    }

    printk("Before ACPI_FLUSH_CPU_CACHE\n");
    ACPI_FLUSH_CPU_CACHE();
    printk("After ACPI_FLUSH_CPU_CACHE\n");

The final few messages of the *new* output *after my amateur mods* on 
the serial console now read as follows:
(XEN) Entering ACPI S5 state.
(XEN) After local_irq_save
(XEN) After spin_debug_disable

There is neither a message reading
(XEN) Some devices failed to power down.
(NOTE: this printk statement however has a XENLOG_ERR before the text - 
so I am not sure whether that should actually appear on the serial 
console at all)
nor one reading
(XEN) Before ACPI_FLUSH_CPU_CACHE

This to me seems to indicate, that the problematic code is somewhere in
between the following lines:
    if ( (error = device_power_down()) )
    {
        printk(XENLOG_ERR "Some devices failed to power down.");
        system_state = SYS_STATE_resume;
        goto done;
    }

I hope that might provide you with some insight which, with your help, 
could be used to make a step forward.
On the other hand I might be completely on the wrong track as I have no 
clue where the actual requested power-down (or as is: reboot) actually 
happens. That was not obvious for me from the code in power.c without 
further knowledge ...
Many thanks in advance for suggestions.

Attachment: XEN console
Description: Text document

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