From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: Powerdown problem on XEN | ACPI S5
Date: Wed, 14 Aug 2013 21:38:33 +0100
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To: Atom2 <ariel.atom2@web2web.at>
Cc: xen-devel <xen-devel@lists.xenproject.org>, Ian Campbell <ian.campbell@citrix.com>, Jan Beulich <JBeulich@suse.com>
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On 14/08/13 21:24, Atom2 wrote:
> Am 14.08.13 22:18, schrieb Andrew Cooper:
> [...]
>>
>> Ok thanks.
>>
>> Do you mind confirming whether S5 works with "iommu=off" on the Xen
>> command line?
>>
>> ~Andrew
>>
> Yes, that works: The system powers off after issuing
>     shutdown -h now
> from the dom0.

So it is certainly an iommu interaction issue, which was sadly suspected
given that we have seen similar problems in the past.

Curiously, there are two IOMMUs on the system.  I am not familiar enough
with Cougar Point chipsets to know how they are layed out.  Perhaps the
ACPI tables might have more information.

ACPI interaction with Xen is tricky at the best of times.  Xen as no AML
interpreter, so relies on Linux in dom0 to most of the ACPI legwork.

My best guess at the moment is that something in the ACPI code for S5 is
turning off enough of the PCH that Xen can no longer talk to the one of
the IOMMUs.

~Andrew