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Re: [Xen-devel] IOMMU Interrupt Remapping query

To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Subject: Re: [Xen-devel] IOMMU Interrupt Remapping query
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Mon, 06 Jun 2011 19:53:56 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Kay, Allen M" <allen.m.kay@xxxxxxxxx>
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Thread-topic: [Xen-devel] IOMMU Interrupt Remapping query
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On 06/06/2011 17:37, "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx> wrote:

> On 06/06/11 16:21, Keir Fraser wrote:
>> On 06/06/2011 15:32, "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx> wrote:
>>> This problem occurs with the XenServer version of 4.1.0 as well as on
>>> xen-unstable at the moment.
>>> Is there any hardware state which is not taken down by the disable
>>> function, any subtle interactions which I have not taken account of?  I
>>> have looked through the source and nothing pops out, but I am out of ideas.
>>> Thanks in advance,
> Attached are the two relevant patches, and two which I don't think are
> relevant but might be if I am wrong.  crash_shutdown was an attempt to
> make an iommu_ops which shut down all iommu functionality without saving
> state.  debug-wip shows where I have put in debug statements.

I think what you need to do ought to be quite similar to the teardown we do
for S3 suspend. Have you considered reusing some of the mechanism in
arch/x86/acpi/power.c? The function device_power_down(), and possibly some
other bits in its caller, would be especially useful I should think. It
already shuts down iommu functionality, turns off x2apic, etc etc. Even if
it is not a perfect fit as is, perhaps it could be fixed up -- it sure looks
similar to what ypu're trying to do. :-)

 -- Keir

> kdump-fix-x2apic and apic-record-boot-mode are also in the source, but I
> believe them to be unrelated to the current problem.
> I have done some further debugging on the assumption that the order of
> shutting down interupt remapping matters with shutting down the lapics
> and ioapics, but disable_qinval causes a panic (qinval.c:222 - "queue
> invalidate wait descriptor was not executed\n") if it is run before both
> the lapics and ioapics are shut down.

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