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

[Le Tan]

2014-06-27 17:55 GMT+08:00 Jan Kiszka <address@hidden>:
> On 2014-06-27 07:46, Le Tan wrote:
>> 2014-06-27 12:55 GMT+08:00 Paolo Bonzini <address@hidden>:
>>> 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...

Yeah, I notice that the third parameter passed to bus->iommu_fn() is
the key. That is the dev->devfn, which is the combination of #device
and #function. I was so careless that I didn't noticed this field. I
think I am getting close to the answer. I will dive into this later.
:）
Thanks very much!

Regards,
Le

>
> Jan
>
>