[Xen-devel] Multi-bridged PCIe devices (Was: Re: iommuu/vt-d issues with LSI MegaSAS (PERC5i))

["Jan Beulich" <JBeulich@xxxxxxxx>]

 >>> On 11.09.13 at 13:05, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
> I found this:
> 
>  http://lists.xen.org/archives/html/xen-devel/2010-06/msg00093.html 
> 
>  while looking for a solution to a similar problem. I am
>  facing a similar issue with LSI (8408E, 3081E-R) and
>  Adaptec (31605) SAS cards. Was there ever a proper, more general
>  fix or workaround for this issue?
> 
>  These SAS cards experience these problems in dom0. When running
>  a vanilla kernel on bare metal, they work OK without intel_iommu
>  set. As soon as I set intel_iommu, the same thing happens (on
>  bare metal, not dom0).
> 
>  Clearly there is something badly broken with multiple layers
>  of bridges when it comes to IOMMU in my setup (Intel 5520 PCIe
>  root hub -> NF200 bridge -> Intel 80333 Bridge -> SAS controller)

The link above has some (hackish) workarounds - did you try
them?

The link above, however, doesn't indicate any relationship to
multiple bridges being in between, so it may not match what
you're observing.

In any event, seeing a hypervisor log with "iommu=debug" might
shed further light on this: For one, we might be able to see which
exact devices are present in the ACPI tables. And we would see
which device(s) eventual faults originate from.

Jan


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