Re: [Xen-devel] IOMMU and AMD 890fx

[Jens Krehbiel-Gräther <xen@xxxxxxxxxxxxxxxxxx>]

Hi!

I know that iommu is only a chipset feature, but it seems that asrock
don't know that... :-(
I will have a look on it when I'm back home (sunday) and then check for
the ACPI tables and the pci device.
I only remember that therewas a kernel message when booting like

"Please activate IOMMU in the bios"

in fact when it is there on 890FX the asrock 890FX Deluxe3 hasn't enabled
it and there is no option for activation in the bios.
I will report on sunday.

Jens

On Thu, 3 Jun 2010 13:51:05 +0200, Andre Przywara <andre.przywara@xxxxxxx>
wrote:
> Hi,
> 
> Jörg is correct, thanks for picking this up. Some additions inline.
> Joerg Roedel wrote:
>> Hello Jens,
>> 
>> On Thu, Jun 03, 2010 at 12:51:23PM +0200, Jens Krehbiel-Gräther wrote:
>>> I got this answer from asrock support:
>>>
>>> <answer>
>>> So, I get more/final answer from Taiwan department:
>>>
>>> For H/W part:
>>> >From chipset spec, RD890(890FX) did support IOMMU.
>>> But IOMMU also need CPU to support.
>> 
>> Thats wrong. The IOMMU is a feature of the chipset northbridge and does
>> not need additional cpu support.
>> 
>>> Till now, AMD has no plan to support
>>> IOMMU on desktop CPU (AM3 socket).
>> 
>> There are AM3 boards out there with server a chipset that have it
>> enabled. Its no question of a socket.
> That would be the Tyan S8005, although the official CPU support list 
> only lists Opteron parts (those in AM3 socket: Suzuka and Budapest)
>> 
>>> It only support with server CPU.
>> 
>> Also wrong. I have seen systems with desktop cpus that have IOMMU
>> enabled (Phenom X4 and Phenom X6).
>> 
>>> For BIOS part:
>> 
>>> AMD has removed IOMMU related registers.
>> 
>> Hard to believe. I have found people in the net who say that the ASUS
>> Crosshair IV mobo has IOMMU support in the BIOS. So if they can enable
>> it, asrock can do that too. Its just the BIOS which has to enable it
> 
> If you want to check this yourself:
> For out-of-the-box support there needs to be an ACPI table called IVRS 
> setup by the BIOS, you can spot this in xm dmesg (or in dmesg on native 
> Linux):
> (XEN) ACPI: IVRS C7E7ACC8, 00E0 (r1  AMD     RD890S  6040000 AMD        
0)
> On a native Linux you can also find the table in
/sys/firmware/acpi/tables
> If the table is present, recent Xen versions (as well as Linux and KVM) 
> should automatically enable and use the IOMMU.
> 
> If the ACPI table is missing, you can try to look for the corresponding 
> PCI device: it should have a vendor/device-id of 1002:5a23, lspci lists 
> it as:
> 00:00.2 Generic system peripheral [0806]: ATI Technologies Inc Device
5a23
> If anyone has a board with the PCI device but a missing ACPI table, 
> please tell us.
> 
> We are already trying to improve the situation, you could help us by 
> reporting the IOMMU support status on 890FX boards. Simply check for the

> ACPI table:
> # xm dmesg | grep IVRS    or
> $ ls /sys/firmware/acpi/tables/IVRS
> and by checking for the PCI device:
> $ /sbin/lspci -d 1002:5a23
> 
> 
> Hope that helps.
> 
> Regards,
> Andre.

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