Re: [Xen-users] powerdown problem on XEN

[Atom2 <ariel.atom2@xxxxxxxxxx>]

Ian,
many thanks for your continued support. I have answers for your latest 
question and probably some more data that might help pinpointing the 
problem further down. Please see below:
Am 13.08.13 22:11, schrieb Ian Campbell:
> On Wed, 2013-08-07 at 15:38 +0200, Atom2 wrote:
>
> > None of the options listed in your link (reboot=b|t|k|n|w|c) managed to
> > turn off power to the system. All but reboot=n (and also noreboot=true)
> > did a reboot after requesting a powerdown with shutdown -h now.
> > reboot=n or noreboot=true just left the machine's power on with the last
> > message on the console (from the gentoo dom0 shutdown) reading
> > [ <no secs since start> ] Power Down.
> [...]
> > I hope the attached file helps in narrowing the powerdown problem down.
> > If you require any more informatio, I'd be more than happy to provide that.
> Hrm, I don't have much in the way bright ideas after this.
>
> It would be worth trying at least Xen 4.3 if not -unstable, just in case
> this has been fixed already.
I have not gone down that route yet, but might do so if everything else 
fails - also in the hope, that 4.3 is not that far away from gentoo ...
> I suppose booting the same Linux kernel natively works and can
> reboot/shutdown as much as you like?
Yes, that works asbolutely reliably - only with XEN do I see those 
powerdown problems ...
> AFAIK xen/arch/x86/acpi/power.c is at least somewhat related to
> linux/drivers/acpi/power.c. I don't know to what extent they have
> diverged but it might be worth eye-balling the diff and/or looking at
> the Linux changelog for likely looking updates.
I did a bit of digging in and comparing of the two files that you 
pointed me to - but unfortunately, they are *VERY* different - not only 
in size (the linux one is around 24k whereas the XEN file is less than 
10k), but also in content. So that not really brought me any further.
I however nevertheless thought I'd modify the XEN power.c file to see 
where the problem may start. I'm far from being a kernel or XEN 
programmer, but I am able to read and basically understand and 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 problem could possibly start:
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 would 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 more information which I could 
use 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 ...
In any case, many thanks in advance.
> Ian.
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