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

[Gordan Bobic <gordan@bobich.net>]

 It looks like I'm definitely not the first person to
 hit this problem:

 http://www.gossamer-threads.com/lists/xen/users/168557?do=post_view_threaded#168557

 No responses or workarounds suggested back then. :(

 Gordan

 On Wed, 11 Sep 2013 12:05:35 +0100, Gordan Bobic <gordan@bobich.net> 
 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)
>
> I tried iommu=dom0-passthrough and it doesn't appear to have
> helped.
>
> I am not seeing similar problems with other PCIe devices that
> are also, in theory doing DMA (e.g. GPUs), but LSI and Adapted
> controllers appear to be affected for some reason.
>
> Is there anything else I could try/do to make this work?
>
> Gordan
>
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