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

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


No responses or workarounds suggested back then. :(


On Wed, 11 Sep 2013 12:05:35 +0100, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
I found this:


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

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?


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