[Xen-devel] Re: AMD iommu , pci passthrough problems assigning devices to HVM

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Hello Wei,

It's an pci express usb3/xhci add-on card, there also seemed to be an alias 
problem with another device, see this thread on LKML, it also contains the 
result of amd_iommu_dump on baremetal 2.6.35 kernel.
At first the kernel didn't boot at all, though xen-unstable did load, so i 
guess there are a few differences in the amd iommu implementation and parsing 
between the linux kernel and xen.

http://lkml.indiana.edu/hypermail/linux/kernel/1008.1/00782.html

Would be nice to have some good explanation of the problem, so i could contact 
MSI to get the bios fixed.

--
Sander



Wednesday, August 11, 2010, 12:11:58 PM, you wrote:

> Hi,
> In your debug output I saw:
> (XEN) AMD-Vi: Fail to find iommu for device04:00.0
> This means no iommu attached to 04:00.0, so it cannot be assigned to any hvm 
> guest. What is this device in your system? An add-on device or on board 
> device? It looks like BIOS failed to create an IVRS entry for this device.

> Wei

> On Tuesday 10 August 2010 14:26:14 Sander Eikelenboom wrote:
>> Hi,
>>
>> I'm running a machine with:
>> - Hypervisor: xen-unstable
>> - Dom0: xen/next-2.6.32.17  commit c3f5aba942c7516a5c76c47345ff0a473daf2542
>>
>> Hardware:
>> -MSI 890FXA-GD70 with AMD IOMMU
>> -Phenom X6
>>
>> I'm trying to do PCI passthrough to a HVM, this fails with:
>>
>> Error: Failed to assign device to IOMMU
>> (0000:04:00.0@100,msitranslate=1,power_mgmt=0) Error: pci: to avoid
>> potential security issue, 0000:08:00.0 is not allowed to be assigned to
>> guest since it is behind PCIe switch that does not support or enable ACS.
>>
>>
>> I have found this thread https://bugzilla.redhat.com/show_bug.cgi?id=526713
>> regarding the ACS problem, which says the pci bridges need these
>> capabilities: ScrValid+, ReqRedir+, CmpltRedir+, and UpstreamFwd+
>>
>> When i do a lspci -vvv on my system i see these capabilities, but i do see
>> some disturbing debug message on boot when amd_iommu_debug is on.
>>
>> Attached:
>> - xm info
>> - xm dmesg (booted with amd_iommu_debug on)
>> - dmesg
>> - lspci -vvv
>>
>> --
>> Sander






-- 
Best regards,
 Sander                            mailto:linux@xxxxxxxxxxxxxx


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