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Re: [Xen-users] AMD-Vi/Intel VT-d: Passthrough or virtualization?

On Tue, 4 Jun 2013 08:32:42 -0400, Nick Khamis <symack@xxxxxxxxx> wrote:
Besides BIOS options another huge problem I encountered was PCI Bridges on boards with lots of PCI Express slots, which are an extra layer and not always compatible with IOMMU. This caused me a lot of headaches when I bought an ASRock Z68 Extreme7 Gen3, as the NF200 PCI Bridge broke all but one PCI Express slot from being IOMMU

NF200 doesn't support ACS, but xen doesn't treat ACS as mandatory. It is disablable
In xend-config.sxp, set:
(pci-passthrough-strict-check no)
(pci-dev-assign-strict-check no)

I am not sure what the correct way to set this for xl is, but xl works
fine for me on my EVGA SR-2 on which ALL 7 PCIe slots are behind NF200
bridges, so mandatory ACS requirement must be disabled by default
or something.

Knowing which controllers on the board map to which devices on the
otherhand is not mentioned in the board manual, so for example the 5 USB controllers on my current board I had to figure out their mappings manually, and one is shared with the
BlueTooth, so that's another hardware concern.

Nothing that cannot be worked out in 5 minutes, though. I did just this
exact thing yesterday with the 12 USB ports on my SR2.

This is very interesting. Could you please explain this a little more.
From what I understand we need to map the PCI bridge back to possible
peripherals (usb, ethernet etc..), that can be sharing resources with
them? Is this also an issue with a board with say 2 PCIe slots vs.

"lspci -t" is usually a good start.


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