Re: [Xen-users] Xen 4.2.1 boot failure with IOMMU enabled

[Andrew Bobulsky <rulerof@xxxxxxxxx>]

Hello Povder,

On Jan 4, 2013, at 1:33 PM, povder <povder@xxxxxxxxx> wrote:

> Hi all
>
> I have a problem with enabling IOMMU on Xen 4.2.1. When I enable it in BIOS
> and in grub.conf using iommu=1 kernel option, my machine cannot boot.
> I get a following error on serial console:
>
> (XEN) ****************************************
> (XEN) Panic on CPU 0:
> (XEN) Xen BUG at pci_amd_iommu.c:35
> (XEN) ****************************************
> (XEN)
> (XEN) Reboot in five seconds...
>
> Error says it is a bug, but maybe there is a workaround for it.

<snip>

> Hardware info:
> Motherboard: M4A89TD PRO USB3 (AMD 890FX chipset)
> CPU: AMD Phenom II X6 1045T
>
> Software info:
> OS: CentOS 6.3 64bit
> Xen: 4.2.1
> BIOS version: 3029 (up to date)

<snip>

It's a shot in the dark, but in my experiences with an MSI board
running the same chipset... Well, really almost every board with that
chipset... IOMMU support wasn't quite ready "out of the gate," and was
usually added and adjusted over time.  In my case, IOMMU had been
added with a BIOS version one or two steps before the version that
shipped with my board.  Between that initial version and the one I
had, they managed to break IOMMU in such a way that it worked with
neither Xen nor ESXi.  That took days to figure out :P

A search of the mailing list brought up a thread from June of 2010,
stating that IOMMU was reported working on the board you have.  You
might want to try a BIOS version that was current at that time, and
work your way forward until it breaks.  The latest BIOS I saw from
that period was 0901.  You could try that and work your way back.

That's the best suggestion I can come up with ;)

Best Regards,
Andrew Bobulsky

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