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

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 2014-01-07 12:15, Jan Beulich wrote:
> > > > On 07.01.14 at 12:35, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
> > On 2014-01-07 11:26, Wu, Feng wrote:
> > > > -----Original Message-----
> > > > From: xen-devel-bounces@xxxxxxxxxxxxx
> > > > [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Gordan Bobic
> > > > Sent: Tuesday, January 07, 2014 6:44 PM
> > > > To: Andrew Cooper
> > > > Cc: xen-devel@xxxxxxxxxxxxx
> > > > Subject: Re: [Xen-devel] Multi-bridged PCIe devices (Was: Re:
> > > > iommuu/vt-d
> > > > issues with LSI MegaSAS (PERC5i))
> > > >
> > > > On 2014-01-07 10:38, Andrew Cooper wrote:
> > > > > 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
> > > >
> > > > I thought this was only applicable to phantom _functions_ (number
> > > > after
> > > > the
> > > > dot) rather than whole phantom _devices_. Is that not the case?
> > > I think that's right. I go through the related code for the pci
> > > phantom device just now, I find that
> > > the information of command line 'pci-phantom' is stored in variable '
> > > phantom_devs[8] '
> > > with type of s truct phantom_dev{}. This variable is used in function
> > > alloc_pdev() as follow:
> > >
> > >
> > >                 for ( i = 0; i < nr_phantom_devs; ++i )
> > >                     if ( phantom_devs[i].seg == pseg->nr &&
> > >                          phantom_devs[i].bus == bus &&
> > >                          phantom_devs[i].slot == PCI_SLOT(devfn) &&
> > >                          phantom_devs[i].stride > PCI_FUNC(devfn) )
> > >                     {
> > >                         pdev->phantom_stride = 
> > > phantom_devs[i].stride;
> > >                         break;
> > >                     }
> > >
> > > So from the code, we can see this command line only works for phantom
> > > _function_, not for whole phantom _devices_.
> > What would it take to make it work for a whole phantom device?
> First and foremost a definition of what a phantom device is and
> how one would behave. Once again - phantom functions are part
> of the PCIe specification, so those don't require a definition.
Konrad's patch from a while back seemed to do the required thing to
allow an otherwise invisible/undetected device to do DMA transfers
without freaking out the IOMMU that doesn't know about it.


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