Re: [Xen-devel] RFC: [PATCH 1/3] Enhance platform support for PCI

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 26/02/15 11:12, Ian Campbell wrote:
>> I have few queries
>>
>> 1) If Dom0 has 'n' ITS nodes, then how does Xen know which virtual ITS
>> command Q is
>>     mapped to which Physical ITS command Q.
>>     In case of linux, the ITS node is added as msi chip to pci using
>> of_pci_msi_chip_add()
>>     and from pci_dev structure we can know which ITS to use.
>>
>>     But in case of Xen, when ITS command is trapped we have only
>> dev_id info from ITS command.
> 
> With the proper PCI infrastructure in place we can map the vdev_id to a
> pdev_id, and from there to our own struct pci_dev 
> 
> The mapping from pdev_id to pci_dev is based on the
> PHYSDEVOP_pci_host_bridge_add and PHYSDEVOP_pci_device_add calls I
> described just now in my mail to Manish in this thread (specifically
> pci_device_add creates and registers struct pci_dev I think).

We may need an hypercall to map the dev_id to a vdev_id.

IIRC, Vijay and Manish was already planned to add one.

> 
>>
>> 2) If DomU is always given one virtual ITS node. If DomU is assinged
>> with two different
>>     PCI devices connected to different physical ITS, then Xen vITS
>> driver should know how to map
>>     PCI device to physical ITS
> 
> Correct, I think that all falls out from the proper tracking of the
> vdev_id to pdev_id and from vits to pits for a given domain and the
> management/tracking of the struct pci_dev.

I think this is the right way to go. Though I haven't read the ITS spec
closely.

Regards,

-- 
Julien Grall

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