Re: [Qemu-devel] About AddressSpace in intel-iommu emulation

[Jan Kiszka <jan.kiszka@web.de>]

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On 2014-06-27 07:46, Le Tan wrote:
> 2014-06-27 12:55 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>> Il 27/06/2014 04:08, Le Tan ha scritto:
>>
>>> 1. In struct IOMMUTLBEntry, I think the addr_mask field should be the
>>> mask of the page offset, right? But I see different usages of this
>>> field. In spapr_tce_translate_iommu(), the addr_mask field is assigned
>>> with the mask of the page offset. However, in pbm_translate_iommu(),
>>> in the passthrough case, the addr_mask field seems to be assigned the
>>> mask of the page number. Is there any problem here?
>>
>>
>> The intended usage is the one of spapr_tce_translate_iommu().  In practice
>> it doesn't matter, both work.
>>
>>
>>> 2. For q35, how to identify origination of DMA requests? The VT-d
>>> manual says we should use source-id(for PCI-Express devices, it is
>>> requester identifier) to map devices to domains. What is the related
>>> part in QEMU? Where can I get the source-id of a DMA request?
>>
>>
>> You need to create a different AddressSpace for each PCI bus or device.
> 
> How to create a different AddressSpace for each device? I thought a
> AddressSpace just belongs to a PCI bus before. The paging structures
> for different functions of the same device can also be different, too.
> So maybe we should create a different AddressSpace for each function?
> How to achieve it? Could you give me some more hints or is there any
> existing example in QEMU?

I would suggest to study the apb IOMMU implementation Paolo referenced
and the PCI layer functions used by that code. Specifically,
pci_setup_iommu takes a callback that is supposed to return an address
space to be used for a particular device. For apb, it's the same for all
devices on a bus, but that's not required...

Jan



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