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

[Gordan Bobic <gordan@bobich.net>]

 On Wed, 11 Sep 2013 14:03:14 +0100, "Jan Beulich" <JBeulich@suse.com> 
 wrote:
>>>> On 11.09.13 at 14:45, Gordan Bobic <gordan@bobich.net> wrote:
>>  dmesg, xl dmesg, lspci -vvvnn and lspci -tvnn output is attached.
>>
>>  I'll try adding one of my LSI cards and see the comparative
>>  behaviour. Right now I don't even know if the phantom device
>>  is on the SAS card or the motherboard.
>
> The Adaptec card being the only thing on bus 0f makes it pretty
> likely that this other device also is on that card.

 That's plausible, but given there are Nvidia NF200 bridges between
 the Intel 5520 PCIe hubs and each of the slots on my motherboard,
 it is not a 100% certainty.

> I guess the issue is mainly because the device itself is a PCI one,
> while the immediately upstream bridge (where I mean only the
> visible one) is PCIe. There _must_ be a PCIe-PCI bridge between
> them. And as long as firmware doesn't know about that bridge
> and the bridge doesn't properly handle config space accesses to
> it, such a device just can't be used with an IOMMU (without some
> yet to be invented workaround).

 You don't think Konrad's patch on the old thread would work
 for getting it working in dom0?

 Gordan