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

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 07/01/14 10:35, Gordan Bobic wrote:
> 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

There is.  See "pci-phantom" in
http://xenbits.xen.org/docs/unstable/misc/xen-command-line.html

~Andrew