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Re: [Xen-devel] Xen 4.0.0-rc7 problem/hang with vt-d DMAR parsing

To: Pasi Kärkkäinen <pasik@xxxxxx>
Subject: Re: [Xen-devel] Xen 4.0.0-rc7 problem/hang with vt-d DMAR parsing
From: Weidong Han <weidong.han@xxxxxxxxx>
Date: Wed, 24 Mar 2010 08:40:16 +0800
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Pasi Kärkkäinen wrote:
On Tue, Mar 23, 2010 at 07:54:33PM +0000, Keir Fraser wrote:
On 23/03/2010 19:37, "Pasi Kärkkäinen" <pasik@xxxxxx> wrote:

It's not impossible that the BIOS VT-d support is just broken (I assume
you've never tested VT-d on this particular type of system before).
Yeah, I've never used VT-d on this system earlier, so it could just be broken
I guess Xen still shouldn't hang on it?
We'd prefer to gracefully disable VT-d.

4.0.0-rc7 (without any extra cmdline options) does disable vt-d and boot ok, after 'hanging' for 30 seconds while parsing the DMAR tables.

If I add "iommu=verbose" option for Xen, then it'll print huge amount of stuff like I pasted earlier.. and it takes forever to print all that.
The BIOS is likely broken. Could you dump the ACPI tables? Then we can confirm if it's BIOS issue. Maybe we can cook a patch to detect this issue (dmaru->address == 0), and handle it more gracefully. I will have a look at it.

Hmm.. wondering if the patch Jan just sent will help with that. Sounds like it might help :)

-- Pasi

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