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RE: [Xen-devel] We still have to disable vtd for old chipset?

To: Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>, Neo Jia <neojia@xxxxxxxxx>, "Kumar, Venkat" <Venkat.Kumar@xxxxxxx>
Subject: RE: [Xen-devel] We still have to disable vtd for old chipset?
From: "Nadolski, Ed" <Ed.Nadolski@xxxxxxx>
Date: Tue, 23 Sep 2008 16:38:58 -0600
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Cc: Keir, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Fraser <keir.fraser@xxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] We still have to disable vtd for old chipset?
May I ask: on the Dell T7400, what kernel parameters do you use in grub.conf to 
enable VT-D?

On my DQ35 mobo with Xen 3.3.0 and CentOS 5.2, I used "kernel /xen-3.3.0.gz 
vtd=1 iommu=1 acpi=force apic=on", and it comes up & NIC passthru works. But 
the same line on my T7400 just crashes very early in the boot with a big hex 

If I set "acpi=off" it boots on the T7400, but I get a VT-D error: 
"intel_iommu_add_device: context mapping failed".

Is this addressed in xen-unstable?  Is there a way to tell if I have the old 
Seaburg chipset?  (This T7400 is pretty new tho.)

Ed Nadolski

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Espen Skoglund
Sent: Tuesday, June 03, 2008 4:50 AM
To: Neo Jia
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Keir Fraser
Subject: Re: [Xen-devel] We still have to disable vtd for old chipset?

I've been using VT-d with a Dell T7400 myself without seeing this
particular problem.  As Keir suggests, I guess you have a pre-retail
version of the machine.  That said, I've had to patch up Xen to get my
version of the chipset working.  There were some bogus values in the
ACPI tables that determined the scope of the IOMMUs.  I'm not sure how
to reliably detect that this problem exists, or whether it's even
worth trying to fix.  I've been waiting for updates that solves the
problem, but there hasn't been anything so far.  I've attached the
patch in case someone else have similar problems.


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