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

[Gordan Bobic <gordan@xxxxxxxxxx>]

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
> > > compatible.
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.
> many?
"lspci -t" is usually a good start.

Gordan

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