Intel IOMMU on Dell Latitude E6400, Lenovo X200 & Dell Precision T5400

Intel IOMMU on Dell Latitude E6400, Lenovo X200 & Dell Precision T5400

[Oleg Orel]

Folks from Intel whi was working on IOMMU support in linux kernel and 
KVM folks who presumably been able to use it successfully, your 
input/comments will be very appriciated.

We are trying to make iommu working on laptops and desctop mentioned in 
the subject line. However, we on all three computers have exactly the 
same problem. We getting interrupt with 2 type of errors reported:

However, we are running into random device DMA issues on all three computers. We are getting MSI-X interrupts from the IOMMUs with 3 types of error reported:

a) PTE doesn't have write bit set
b) PTE doesn't have read bit set
c) Present bit in root entry is clear


We had reported more details @ 
https://bugzilla.redhat.com/show_bug.cgi?id=479996 and 
http://bugzilla.kernel.org/show_bug.cgi?id=11821


Please advice us a way to debug it, what peaces should we look at, 
print/check, etc...

1. Could we blame BIOS for that?
2. Is it possible that we build kernel with options what conflicting 
with iommu implementation in some way? If so, could you share your 
binary/source/config what works for you?
3. What desktop/laptops been tested and you aware that it works?
4. KVM folks, is it KVM+IOMMU works?
5. We have been seeing this issue with the latest Linus' git kernel as 
well as 2.6.29-rc3 from kernel.org.
Oleg

RE: Intel IOMMU on Dell Latitude E6400, Lenovo X200 & Dell Precision T5400

[Yu, Fenghua]

>We had reported more details @
>https://bugzilla.redhat.com/show_bug.cgi?id=479996 and
>http://bugzilla.kernel.org/show_bug.cgi?id=11821

Look into http://bugzilla.kernel.org/show_bug.cgi?id=11821
and find that:

wlan0: Failed to config new SSID to the low-level driver
BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
IP: [<ffffffff8037cf1f>] pci_find_upstream_pcie_bridge+0x1f/0xa0
...
[<ffffffff80386808>] get_domain_for_dev+0x58/0x620
 [<ffffffff8029574d>] ? __alloc_pages_internal+0xed/0x4f0
 [<ffffffff803870f8>] get_valid_domain_for_dev+0x18/0x150
 [<ffffffff803875e7>] intel_map_single+0x47/0x160
 [<ffffffff802b8726>] ? alloc_pages_current+0x76/0xf0
 [<ffffffff8038777f>] intel_alloc_coherent+0x7f/0xb0
...

Wireless LAN could cause the NULL pointer access in get_domain_for_dev() which is IOMMU function.

As an experiment, could you disable wireless lan on your machine and try to boot IOMMU kernel?

Thanks.

-Fenghua

Re: Intel IOMMU on Dell Latitude E6400, Lenovo X200 & Dell Precision T5400

[Oleg Orel]

Yu, Fenghua wrote:
>   
>> We had reported more details @
>> https://bugzilla.redhat.com/show_bug.cgi?id=479996 and
>> http://bugzilla.kernel.org/show_bug.cgi?id=11821
>>     
>
> Look into http://bugzilla.kernel.org/show_bug.cgi?id=11821
> and find that:
>
> wlan0: Failed to config new SSID to the low-level driver
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
> IP: [<ffffffff8037cf1f>] pci_find_upstream_pcie_bridge+0x1f/0xa0
> ...
> [<ffffffff80386808>] get_domain_for_dev+0x58/0x620
>  [<ffffffff8029574d>] ? __alloc_pages_internal+0xed/0x4f0
>  [<ffffffff803870f8>] get_valid_domain_for_dev+0x18/0x150
>  [<ffffffff803875e7>] intel_map_single+0x47/0x160
>  [<ffffffff802b8726>] ? alloc_pages_current+0x76/0xf0
>  [<ffffffff8038777f>] intel_alloc_coherent+0x7f/0xb0
> ...
>
> Wireless LAN could cause the NULL pointer access in get_domain_for_dev() which is IOMMU function.
>
> As an experiment, could you disable wireless lan on your machine and try to boot IOMMU kernel?
>
> Thanks.
>
> -Fenghua
>   
Yu,
I did it already yesterday. It didn't help. It fact I had disable all 
disableble devices, also, on T5400 when is failing as well, we do not 
have a wireless.