Re: [Xen-devel] [RFC 6/6] acpi:arm64: Add support for parsing IORT table

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.06.17 at 15:36, <julien.grall@xxxxxxx> wrote:
> On 09/06/17 12:15, Robin Murphy wrote:
>> On 08/06/17 20:30, Sameer Goel wrote:
>> [...]
>>>  /**
>>> - * iort_iommu_configure - Set-up IOMMU configuration for a device.
>>> + * iort_iommu_configure - Set-up IOMMU configuration for a device. This
>>> + * function sets up the fwspec as needed for a given device. Only PCI
>>> + * devices are supported for now.
>>>   *
>>>   * @dev: device to configure
>>>   *
>>> - * Returns: iommu_ops pointer on configuration success
>>> - *          NULL on configuration failure
>>> + * Returns: Appropriate acpi_status
>>>   */
>>> -const struct iommu_ops *iort_iommu_configure(struct device *dev)
>>> +acpi_status iort_iommu_configure(struct device *dev)
>>>  {
>>>     struct acpi_iort_node *node, *parent;
>>> -   const struct iommu_ops *ops = NULL;
>>>     u32 streamid = 0;
>>> +   acpi_status status = AE_OK;
>>>
>>>     if (dev_is_pci(dev)) {
>>> -           struct pci_bus *bus = to_pci_dev(dev)->bus;
>>> +           struct pci_dev *pci_device = to_pci_dev(dev);
>>>             u32 rid;
>>>
>>> -           pci_for_each_dma_alias(to_pci_dev(dev), __get_pci_rid,
>>> -                                  &rid);
>>> +           rid = PCI_BDF2(pci_device->bus,pci_device->devfn);
>>
>> Beware that the Linux code isn't actually correct to begin with[1]. I
>> don't know how much Xen deals with PCI bridges and quirks, but as it
>> stands you should be able to trivially expose the flaw here by plugging
>> in a Marvell 88SE912x-based SATA card and watching either DMA or MSIs
>> (or even both) kick up stream table faults.
>>
>> Robin.
>>
>> [1]:http://www.spinics.net/lists/linux-acpi/msg74844.html 
> 
> I am not sure how x86 is handling that. The closest I can find would be 
> domain_context_mapping. I have CCed x86 folks to get more feedback here.

I'm lacking enough context to know whether this is the issue
with what we call phantom devices, or something else.

Jan


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