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

[Gordan Bobic <gordan@bobich.net>]

On 2014-01-07 03:17, Zhang, Yang Z wrote:
> Konrad Rzeszutek Wilk wrote on 2014-01-07:
>>> Which would look like this:
>>> 
>>> C220 ---> Tundra Bridge -----> (HB6 PCI bridge -> Brooktree BDFs) on 
>>> the card
>>> 	      \--------------> IEEE-1394a
>>> 
>>> I am actually wondering if this 07:00.0 device is the one that
>>> reports itself as 08:00.0 (which I think is what you alluding to
>>> Jan)
>>> 
>> 
>> And to double check that theory I decided to pass in the IEEE-1394a to 
>> a guest:
>> 
>>            +-1c.5-[07-08]----00.0-[08]----03.0  Texas Instruments
>> TSB43AB22A IEEE-1394a-2000 Controller (PHY/Link) [iOHCI-Lynx]
>> 
>> 
>> (XEN) [VT-D]iommu.c:885: iommu_fault_status: Fault Overflow (XEN)
>> [VT-D]iommu.c:887: iommu_fault_status: Primary Pending Fault (XEN)
>> [VT-D]iommu.c:865: DMAR:[DMA Read] Request device [0000:08:00.0] fault
>> addr 370f1000, iommu reg = ffff82c3ffd53000 (XEN) DMAR:[fault reason
>> 02h] Present bit in context entry is clear (XEN) print_vtd_entries:
>> iommu ffff83083d4939b0 dev 0000:08:00.0 gmfn 370f1 (XEN)     
>> root_entry
>> = ffff83083d47f000 (XEN)     root_entry[8] = 72569b001 (XEN)     
>> context
>> = ffff83072569b000 (XEN)     context[0] = 0_0 (XEN)     ctxt_entry[0]
>> not present
>> 
>> So, capture card OK - Likely the Tundra bridge has an issue:
>> 
>> 07:00.0 PCI bridge: Tundra Semiconductor Corp. Device 8113 (rev 01)
>> (prog-if 01 [Subtractive decode])
>>         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
>>         ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz-
>>         UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort+
>>         >SERR- <PERR- INTx- Latency: 0 Bus: primary=07, secondary=08,
>>         subordinate=08, sec-latency=32 Memory behind bridge:
>>         f0600000-f06fffff Secondary status: 66MHz+ FastB2B+ ParErr-
>>         DEVSEL=medium TAbort- <TAbort- <MAbort+ <SERR- <PERR- 
>> BridgeCtl:
>>         Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
>>                 PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
>>         Capabilities: [60] Subsystem: Super Micro Computer Inc Device 
>> 0805
>>         Capabilities: [a0] Power Management version 3
>>                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
>>                 PME(D0+,D1+,D2+,D3hot+,D3cold+) Status: D0 NoSoftRst+
>>                 PME-Enable- DSel=0 DScale=0 PME-
>> 
>> or there is some unknown bridge in the motherboard.
> 
> According your description above, the upstream Linux should also have
> the same problem. Did you see it with upstream Linux?

The problem I was seeing with LSI cards (phantom device doing DMA)
does, indeed, also occur in upstream Linux. If I enable intel-iommu on
bare metal Linux, the same problem occurs as with Xen.

> There may be some buggy device that generate DMA request with internal
> BDF but it didn't expose it(not like Phantom device). For those
> devices, I think we need to setup the VT-d page table manually.

I think what is needed is a pci-phantom style override that tells the
hypervisor to tell the IOMMU to allow DMA traffic from a specific
invisible device ID.

Gordan