linux-kernel - Re: [PATCH] PCI: quirks: DMA alias quirk for Adaptec 3405

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Message-ID: <1422052241.4048.14.camel@redhat.com>
Date:	Fri, 23 Jan 2015 15:30:41 -0700
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	linux-pci@...r.kernel.org, aacraid@...ptec.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: quirks: DMA alias quirk for Adaptec 3405

On Fri, 2015-01-23 at 15:50 -0600, Bjorn Helgaas wrote:
> On Tue, Jan 13, 2015 at 11:26:50AM -0700, Alex Williamson wrote:
> > As noted in the added comment, this device is actually an Intel 80333
> > I/O processor where the exposed device at 0e.0 is actually the address
> > translation unit of the I/O processor and a hidden, private device at
> > 01.0 masters the DMA for the device.  In order to enable the IOMMU, we
> > therefore need to create a fixed alias between the exposed and hidden
> > devfn.
> > 
> > Scenarios like this are potentially likely for any device incorporating
> > this I/O processor, so this little bit of abstraction with the fixed
> > alias table should make future additions trivial.
> 
> This sounds like the result of some serious debugging :)  Do you have a
> pointer to a bugzilla or some email discussion?  I'd like to make the fix
> discoverable starting with a failure symptom.

Sorry, this one comes from a private bugzilla.  The symptom is simply a
slew of IOMMU faults when trying to boot the system with the IOMMU
enabled.  For example, with the Adaptec 3405 showing up at 02:0e.0 on an
Intel system, the log is filled with:

dmar: DRHD: handling fault status reg 3
dmar: DMAR:[DMA Write] Request device [02:01.0] fault addr ffbff000 
DMAR:[fault reason 02] Present bit in context entry is clear
dmar: DRHD: handling fault status reg 3
dmar: DMAR:[DMA Write] Request device [02:01.0] fault addr ffbfe000 
DMAR:[fault reason 02] Present bit in context entry is clear

As expected, the device is non-functional.  In the log I have there are
only DMA write faults and the addresses are all ffbxxxxx, which falls
into a reserved memory area on the system and owned by a PNP0c02 device
according to iomem.  With the change here the device, of course, works
without any issues with VT-d enabled.  Thanks,

Alex

> > Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> > Cc: Adaptec OEM Raid Solutions <aacraid@...ptec.com>
> > ---
> > 
> >  drivers/pci/quirks.c |   37 +++++++++++++++++++++++++++++++++++++
> >  1 file changed, 37 insertions(+)
> > 
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index ed6f89b..19bdb17 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -3528,6 +3528,43 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_JMICRON,
> >  			 quirk_dma_func1_alias);
> >  
> >  /*
> > + * Some devices DMA with the wrong devfn, not just the wrong function.
> > + * quirk_fixed_dma_alias() uses this table to create fixed aliass, where
> > + * the alias is "fixed" and independent of the device devfn.
> > + *
> > + * For example, the Adaptec 3405 is a PCIe card making use of an Intel 80333
> > + * I/O processor.  To software, this appears as a straightforward PCIe-to-PCI/X
> > + * bridge with a single device on the subordinate bus.  In reality, the exposed
> > + * device at 0e.0 is the Address Translation Unit (ATU) of the controller that
> > + * provides a bridge to the internal bus of the I/O processor.  The controller
> > + * supports private devices, which can be hidden from PCI config space.  In the
> > + * case of the Adaptec 3405, a private device at 01.0 appears to be the DMA
> > + * engine, which therefore needs to become a DMA alias for the device.
> > + */
> > +static const struct pci_device_id fixed_dma_alias_tbl[] = {
> > +	{ PCI_DEVICE_SUB(PCI_VENDOR_ID_ADAPTEC2, 0x0285,
> > +			 PCI_VENDOR_ID_ADAPTEC2, 0x02bb), /* Adaptec 3405 */
> > +	  .driver_data = PCI_DEVFN(1, 0) },
> > +	{ 0 }
> > +};
> > +
> > +static void quirk_fixed_dma_alias(struct pci_dev *dev)
> > +{
> > +	const struct pci_device_id *id;
> > +
> > +	id = pci_match_id(fixed_dma_alias_tbl, dev);
> > +	if (id) {
> > +		dev->dma_alias_devfn = id->driver_data;
> > +		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
> > +		dev_info(&dev->dev, "Enabling fixed DMA alias to %02x.%d\n",
> > +			 PCI_SLOT(dev->dma_alias_devfn),
> > +			 PCI_FUNC(dev->dma_alias_devfn));
> > +	}
> > +}
> > +
> > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ADAPTEC2, 0x0285, quirk_fixed_dma_alias);
> > +
> > +/*
> >   * A few PCIe-to-PCI bridges fail to expose a PCIe capability, resulting in
> >   * using the wrong DMA alias for the device.  Some of these devices can be
> >   * used as either forward or reverse bridges, so we need to test whether the
> > 
> --
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